WIP: Integration test for contact list worker

Tolerate 404 responses due to missing folders

See merge request briar/briar!1692

CONTRIBUTING.md

@@ -0,0 +1,10 @@
+Folder-Description:
+===================
+* `briar-*`: Specifically for the Briar app (Phone/Desktop/Headless)
+* `bramble-*`: The protocol stack - not necessarily Briar-dependent
+
+---
+
+* `*-api`: public stuff that can be referenced from other packages and modules - mostly interfaces + a few utility classes
+* `*-core`: implementations of api that are portable across Android/Desktop/Headless
+* `*-java`: implementations of api that are specific to Desktop & Headless

bramble-android/build.gradle

@@ -15,8 +15,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 30
-		versionCode 10408
-		versionName "1.4.8"
+		versionCode 10410
+		versionName "1.4.10"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

bramble-api/src/main/java/org/briarproject/bramble/api/connection/ConnectionManager.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 @NotNullByDefault
 public interface ConnectionManager {
@@ -45,6 +46,14 @@ public interface ConnectionManager {
 	void manageOutgoingConnection(ContactId c, TransportId t,
 			TransportConnectionWriter w);
 
+	/**
+	 * Manages an outgoing connection to a contact via a mailbox. The IDs of
+	 * any messages sent or acked are added to the given
+	 * {@link OutgoingSessionRecord}.
+	 */
+	void manageOutgoingConnection(ContactId c, TransportId t,
+			TransportConnectionWriter w, OutgoingSessionRecord sessionRecord);
+
 	/**
 	 * Manages an outgoing connection to a contact over a duplex transport.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -126,16 +126,11 @@ public interface DatabaseComponent extends TransactionManager {
 			TransportKeys k) throws DbException;
 
 	/**
-	 * Returns true if there are any acks or messages to send to the given
-	 * contact over a transport with the given maximum latency.
+	 * Returns true if there are any acks to send to the given contact.
 	 * <p/>
 	 * Read-only.
-	 *
-	 * @param eager True if messages that are not yet due for retransmission
-	 * should be included
 	 */
-	boolean containsAnythingToSend(Transaction txn, ContactId c,
-			long maxLatency, boolean eager) throws DbException;
+	boolean containsAcksToSend(Transaction txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact for the given
@@ -161,6 +156,18 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	boolean containsIdentity(Transaction txn, AuthorId a) throws DbException;
 
+	/**
+	 * Returns true if there are any messages to send to the given contact
+	 * over a transport with the given maximum latency.
+	 * <p/>
+	 * Read-only.
+	 *
+	 * @param eager True if messages that are not yet due for retransmission
+	 * should be included
+	 */
+	boolean containsMessagesToSend(Transaction txn, ContactId c,
+			long maxLatency, boolean eager) throws DbException;
+
 	/**
 	 * Returns true if the database contains the given pending contact.
 	 * <p/>
@@ -534,15 +541,18 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	long getNextCleanupDeadline(Transaction txn) throws DbException;
 
-	/*
+	/**
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE if
-	 * no messages are scheduled to be sent.
+	 * message is due to be sent to the given contact over a transport with
+	 * the given latency.
+	 * <p>
+	 * The returned value may be zero if a message is due to be sent
+	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(Transaction txn, ContactId c) throws DbException;
+	long getNextSendTime(Transaction txn, ContactId c, long maxLatency)
+			throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -37,8 +37,14 @@ public interface LifecycleManager {
 	 */
 	enum LifecycleState {
 
-		STARTING, MIGRATING_DATABASE, COMPACTING_DATABASE, STARTING_SERVICES,
-		RUNNING, STOPPING;
+		CREATED,
+		STARTING,
+		MIGRATING_DATABASE,
+		COMPACTING_DATABASE,
+		STARTING_SERVICES,
+		RUNNING,
+		STOPPING,
+		STOPPED;
 
 		public boolean isAfter(LifecycleState state) {
 			return ordinal() > state.ordinal();

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxConstants.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import java.util.List;
 
 import static java.util.Collections.singletonList;
+import static java.util.concurrent.TimeUnit.DAYS;
 import static java.util.concurrent.TimeUnit.HOURS;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_FRAME_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
@@ -65,4 +66,8 @@ public interface MailboxConstants {
 	 */
 	long PROBLEM_MS_SINCE_LAST_SUCCESS = HOURS.toMillis(1);
 
+	/**
+	 * The maximum latency of the mailbox transport in milliseconds.
+	 */
+	long MAX_LATENCY = DAYS.toMillis(14);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxId.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.api.mailbox;
 
 import com.fasterxml.jackson.annotation.JsonValue;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.UniqueId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
@@ -32,7 +33,7 @@ public abstract class MailboxId extends UniqueId {
 		}
 		try {
 			return fromHexString(token);
-		} catch (IllegalArgumentException e) {
+		} catch (FormatException e) {
 			throw new InvalidMailboxIdException();
 		}
 	}

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxProperties.java

@@ -11,7 +11,7 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class MailboxProperties {
 
-	private final String baseUrl;
+	private final String onion;
 	private final MailboxAuthToken authToken;
 	private final boolean owner;
 	private final List<MailboxVersion> serverSupports;
@@ -23,9 +23,9 @@ public class MailboxProperties {
 	/**
 	 * Constructor for properties used by the mailbox's owner.
 	 */
-	public MailboxProperties(String baseUrl, MailboxAuthToken authToken,
+	public MailboxProperties(String onion, MailboxAuthToken authToken,
 			List<MailboxVersion> serverSupports) {
-		this.baseUrl = baseUrl;
+		this.onion = onion;
 		this.authToken = authToken;
 		this.owner = true;
 		this.serverSupports = serverSupports;
@@ -36,10 +36,10 @@ public class MailboxProperties {
 	/**
 	 * Constructor for properties used by a contact of the mailbox's owner.
 	 */
-	public MailboxProperties(String baseUrl, MailboxAuthToken authToken,
+	public MailboxProperties(String onion, MailboxAuthToken authToken,
 			List<MailboxVersion> serverSupports, MailboxFolderId inboxId,
 			MailboxFolderId outboxId) {
-		this.baseUrl = baseUrl;
+		this.onion = onion;
 		this.authToken = authToken;
 		this.owner = false;
 		this.serverSupports = serverSupports;
@@ -47,13 +47,11 @@ public class MailboxProperties {
 		this.outboxId = outboxId;
 	}
 
-	public String getBaseUrl() {
-		return baseUrl;
-	}
-
+	/**
+	 * Returns the onion address of the mailbox, excluding the .onion suffix.
+	 */
 	public String getOnion() {
-		return baseUrl.replaceFirst("^http://", "")
-				.replaceFirst("\\.onion$", "");
+		return onion;
 	}
 
 	public MailboxAuthToken getAuthToken() {

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxSettingsManager.java

@@ -35,6 +35,9 @@ public interface MailboxSettingsManager {
 	void recordSuccessfulConnection(Transaction txn, long now)
 			throws DbException;
 
+	void recordSuccessfulConnection(Transaction txn, long now,
+			List<MailboxVersion> versions) throws DbException;
+
 	void recordFailedConnectionAttempt(Transaction txn, long now)
 			throws DbException;
 

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxUpdateManager.java

@@ -29,19 +29,35 @@ public interface MailboxUpdateManager {
 
 	/**
 	 * The number of properties required for an update message with a mailbox.
+	 * <p>
+	 * The required properties are {@link #PROP_KEY_ONION},
+	 * {@link #PROP_KEY_AUTHTOKEN}, {@link #PROP_KEY_INBOXID} and
+	 * {@link #PROP_KEY_OUTBOXID}.
 	 */
 	int PROP_COUNT = 4;
 
 	/**
-	 * The required properties of an update message with a mailbox.
+	 * The onion address of the mailbox, excluding the .onion suffix.
 	 */
 	String PROP_KEY_ONION = "onion";
+
+	/**
+	 * A bearer token for accessing the mailbox (64 hex digits).
+	 */
 	String PROP_KEY_AUTHTOKEN = "authToken";
+
+	/**
+	 * A folder ID for downloading messages (64 hex digits).
+	 */
 	String PROP_KEY_INBOXID = "inboxId";
+
+	/**
+	 * A folder ID for uploading messages (64 hex digits).
+	 */
 	String PROP_KEY_OUTBOXID = "outboxId";
 
 	/**
-	 * Length of the Onion property.
+	 * Length of the {@link #PROP_KEY_ONION} property.
 	 */
 	int PROP_ONION_LENGTH = 56;
 
@@ -63,9 +79,26 @@ public interface MailboxUpdateManager {
 	 */
 	String GROUP_KEY_SENT_CLIENT_SUPPORTS = "sentClientSupports";
 
+	/**
+	 * Returns the latest {@link MailboxUpdate} sent to the given contact.
+	 * <p>
+	 * If we have our own mailbox then the update will be a
+	 * {@link MailboxUpdateWithMailbox} containing the
+	 * {@link MailboxProperties} the contact should use for communicating with
+	 * our mailbox.
+	 */
 	MailboxUpdate getLocalUpdate(Transaction txn, ContactId c)
 			throws DbException;
 
+	/**
+	 * Returns the latest {@link MailboxUpdate} received from the given
+	 * contact, or null if no update has been received.
+	 * <p>
+	 * If the contact has a mailbox then the update will be a
+	 * {@link MailboxUpdateWithMailbox} containing the
+	 * {@link MailboxProperties} we should use for communicating with the
+	 * contact's mailbox.
+	 */
 	@Nullable
 	MailboxUpdate getRemoteUpdate(Transaction txn, ContactId c)
 			throws DbException;

bramble-api/src/main/java/org/briarproject/bramble/api/sync/DeferredSendHandler.java

@@ -1,15 +0,0 @@
-package org.briarproject.bramble.api.sync;
-
-import java.util.Collection;
-
-/**
- * An interface for holding the IDs of messages sent and acked during an
- * outgoing {@link SyncSession} so they can be recorded in the DB as sent
- * or acked at some later time.
- */
-public interface DeferredSendHandler {
-
-	void onAckSent(Collection<MessageId> acked);
-
-	void onMessageSent(MessageId sent);
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/OutgoingSessionRecord.java

@@ -0,0 +1,37 @@
+package org.briarproject.bramble.api.sync;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.Collection;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * A container for holding the IDs of messages sent and acked during an
+ * outgoing {@link SyncSession}, so they can be recorded in the DB as sent
+ * or acked at some later time.
+ */
+@ThreadSafe
+@NotNullByDefault
+public class OutgoingSessionRecord {
+
+	private final Collection<MessageId> ackedIds = new CopyOnWriteArrayList<>();
+	private final Collection<MessageId> sentIds = new CopyOnWriteArrayList<>();
+
+	public void onAckSent(Collection<MessageId> acked) {
+		ackedIds.addAll(acked);
+	}
+
+	public void onMessageSent(MessageId sent) {
+		sentIds.add(sent);
+	}
+
+	public Collection<MessageId> getAckedIds() {
+		return ackedIds;
+	}
+
+	public Collection<MessageId> getSentIds() {
+		return sentIds;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncSessionFactory.java

@@ -12,12 +12,30 @@ import javax.annotation.Nullable;
 @NotNullByDefault
 public interface SyncSessionFactory {
 
+	/**
+	 * Creates a session for receiving data from a contact.
+	 */
 	SyncSession createIncomingSession(ContactId c, InputStream in,
 			PriorityHandler handler);
 
+	/**
+	 * Creates a session for sending data to a contact over a simplex transport.
+	 *
+	 * @param eager True if messages should be sent eagerly, ie regardless of
+	 * whether they're due for retransmission.
+	 */
 	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, boolean eager, StreamWriter streamWriter);
 
+	/**
+	 * Creates a session for sending data to a contact via a mailbox. The IDs
+	 * of any messages sent or acked will be added to the given
+	 * {@link OutgoingSessionRecord}.
+	 */
+	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
+			long maxLatency, StreamWriter streamWriter,
+			OutgoingSessionRecord sessionRecord);
+
 	SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, int maxIdleTime, StreamWriter streamWriter,
 			@Nullable Priority priority);

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/GroupVisibilityUpdatedEvent.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.api.sync.event;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.Group.Visibility;
 
 import java.util.Collection;
 
@@ -15,12 +16,19 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class GroupVisibilityUpdatedEvent extends Event {
 
+	private final Visibility visibility;
 	private final Collection<ContactId> affected;
 
-	public GroupVisibilityUpdatedEvent(Collection<ContactId> affected) {
+	public GroupVisibilityUpdatedEvent(Visibility visibility,
+			Collection<ContactId> affected) {
+		this.visibility = visibility;
 		this.affected = affected;
 	}
 
+	public Visibility getVisibility() {
+		return visibility;
+	}
+
 	/**
 	 * Returns the contacts affected by the update.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -40,7 +40,7 @@ public class IoUtils {
 		}
 	}
 
-	private static void delete(File f) {
+	public static void delete(File f) {
 		if (!f.delete() && LOG.isLoggable(WARNING))
 			LOG.warning("Could not delete " + f.getAbsolutePath());
 	}

bramble-api/src/main/java/org/briarproject/bramble/util/StringUtils.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.util;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.io.UnsupportedEncodingException;
@@ -95,10 +96,10 @@ public class StringUtils {
 	/**
 	 * Converts the given hex string to a byte array.
 	 */
-	public static byte[] fromHexString(String hex) {
+	public static byte[] fromHexString(String hex) throws FormatException {
 		int len = hex.length();
 		if (len % 2 != 0)
-			throw new IllegalArgumentException("Not a hex string");
+			throw new FormatException();
 		byte[] bytes = new byte[len / 2];
 		for (int i = 0, j = 0; i < len; i += 2, j++) {
 			int high = hexDigitToInt(hex.charAt(i));
@@ -108,11 +109,11 @@ public class StringUtils {
 		return bytes;
 	}
 
-	private static int hexDigitToInt(char c) {
+	private static int hexDigitToInt(char c) throws FormatException {
 		if (c >= '0' && c <= '9') return c - '0';
 		if (c >= 'A' && c <= 'F') return c - 'A' + 10;
 		if (c >= 'a' && c <= 'f') return c - 'a' + 10;
-		throw new IllegalArgumentException("Not a hex digit: " + c);
+		throw new FormatException();
 	}
 
 	public static String trim(String s) {
@@ -130,13 +131,13 @@ public class StringUtils {
 		return MAC.matcher(mac).matches();
 	}
 
-	public static byte[] macToBytes(String mac) {
-		if (!MAC.matcher(mac).matches()) throw new IllegalArgumentException();
+	public static byte[] macToBytes(String mac) throws FormatException {
+		if (!MAC.matcher(mac).matches()) throw new FormatException();
 		return fromHexString(mac.replaceAll(":", ""));
 	}
 
-	public static String macToString(byte[] mac) {
-		if (mac.length != 6) throw new IllegalArgumentException();
+	public static String macToString(byte[] mac) throws FormatException {
+		if (mac.length != 6) throw new FormatException();
 		StringBuilder s = new StringBuilder();
 		for (byte b : mac) {
 			if (s.length() > 0) s.append(':');

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -230,14 +230,14 @@ public class TestUtils {
 
 	public static MailboxProperties getMailboxProperties(boolean owner,
 			List<MailboxVersion> serverSupports) {
-		String baseUrl = "http://" + getRandomString(56) + ".onion"; // TODO
+		String onion = getRandomString(56);
 		MailboxAuthToken authToken = new MailboxAuthToken(getRandomId());
 		if (owner) {
-			return new MailboxProperties(baseUrl, authToken, serverSupports);
+			return new MailboxProperties(onion, authToken, serverSupports);
 		}
 		MailboxFolderId inboxId = new MailboxFolderId(getRandomId());
 		MailboxFolderId outboxId = new MailboxFolderId(getRandomId());
-		return new MailboxProperties(baseUrl, authToken, serverSupports,
+		return new MailboxProperties(onion, authToken, serverSupports,
 				inboxId, outboxId);
 	}
 

bramble-core/build.gradle

@@ -16,7 +16,7 @@ dependencies {
 	implementation 'org.bitlet:weupnp:0.1.4'
 	implementation 'net.i2p.crypto:eddsa:0.2.0'
 	implementation 'org.whispersystems:curve25519-java:0.5.0'
-	implementation 'org.briarproject:jtorctl:0.4'
+	implementation 'org.briarproject:jtorctl:0.5'
 
 	//noinspection GradleDependency
 	implementation "com.squareup.okhttp3:okhttp:$okhttp_version"

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.account;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.account.AccountManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.DecryptionException;
@@ -209,7 +210,13 @@ class AccountManagerImpl implements AccountManager {
 			LOG.warning("Failed to load encrypted database key");
 			throw new DecryptionException(INVALID_CIPHERTEXT);
 		}
-		byte[] ciphertext = fromHexString(hex);
+		byte[] ciphertext;
+		try {
+			ciphertext = fromHexString(hex);
+		} catch (FormatException e) {
+			LOG.warning("Encrypted database key has invalid format");
+			throw new DecryptionException(INVALID_CIPHERTEXT);
+		}
 		KeyStrengthener keyStrengthener = databaseConfig.getKeyStrengthener();
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -456,8 +456,7 @@ class ClientHelperImpl implements ClientHelper {
 		checkLength(inboxId, UniqueId.LENGTH);
 		byte[] outboxId = properties.getRaw(PROP_KEY_OUTBOXID);
 		checkLength(outboxId, UniqueId.LENGTH);
-		String baseUrl = "http://" + onion + ".onion"; // TODO
-		MailboxProperties props = new MailboxProperties(baseUrl,
+		MailboxProperties props = new MailboxProperties(onion,
 				new MailboxAuthToken(authToken), serverSupportsList,
 				new MailboxFolderId(inboxId), new MailboxFolderId(outboxId));
 		return new MailboxUpdateWithMailbox(clientSupportsList, props);

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionManagerImpl.java

@@ -13,6 +13,7 @@ import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
@@ -100,7 +101,16 @@ class ConnectionManagerImpl implements ConnectionManager {
 			TransportConnectionWriter w) {
 		ioExecutor.execute(new OutgoingSimplexSyncConnection(keyManager,
 				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, c, t, w));
+				syncSessionFactory, transportPropertyManager, c, t, w, null));
+	}
+
+	@Override
+	public void manageOutgoingConnection(ContactId c, TransportId t,
+			TransportConnectionWriter w, OutgoingSessionRecord sessionRecord) {
+		ioExecutor.execute(new OutgoingSimplexSyncConnection(keyManager,
+				connectionRegistry, streamReaderFactory, streamWriterFactory,
+				syncSessionFactory, transportPropertyManager, c, t, w,
+				sessionRecord));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingSimplexSyncConnection.java

@@ -6,6 +6,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
@@ -16,6 +17,8 @@ import org.briarproject.bramble.api.transport.StreamWriterFactory;
 
 import java.io.IOException;
 
+import javax.annotation.Nullable;
+
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -26,6 +29,8 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 	private final ContactId contactId;
 	private final TransportId transportId;
 	private final TransportConnectionWriter writer;
+	@Nullable
+	private final OutgoingSessionRecord sessionRecord;
 
 	OutgoingSimplexSyncConnection(KeyManager keyManager,
 			ConnectionRegistry connectionRegistry,
@@ -34,13 +39,15 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 			SyncSessionFactory syncSessionFactory,
 			TransportPropertyManager transportPropertyManager,
 			ContactId contactId, TransportId transportId,
-			TransportConnectionWriter writer) {
+			TransportConnectionWriter writer,
+			@Nullable OutgoingSessionRecord sessionRecord) {
 		super(keyManager, connectionRegistry, streamReaderFactory,
 				streamWriterFactory, syncSessionFactory,
 				transportPropertyManager);
 		this.contactId = contactId;
 		this.transportId = transportId;
 		this.writer = writer;
+		this.sessionRecord = sessionRecord;
 	}
 
 	@Override
@@ -71,10 +78,16 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
 				w.getOutputStream(), ctx);
 		ContactId c = requireNonNull(ctx.getContactId());
-		// Use eager retransmission if the transport is lossy and cheap
-		return syncSessionFactory.createSimplexOutgoingSession(c,
-				ctx.getTransportId(), w.getMaxLatency(), w.isLossyAndCheap(),
-				streamWriter);
+		if (sessionRecord == null) {
+			// Use eager retransmission if the transport is lossy and cheap
+			return syncSessionFactory.createSimplexOutgoingSession(c,
+					ctx.getTransportId(), w.getMaxLatency(),
+					w.isLossyAndCheap(), streamWriter);
+		} else {
+			return syncSessionFactory.createSimplexOutgoingSession(c,
+					ctx.getTransportId(), w.getMaxLatency(), streamWriter,
+					sessionRecord);
+		}
 	}
 }
 

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -163,16 +163,11 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns true if there are any acks or messages to send to the given
-	 * contact over a transport with the given maximum latency.
+	 * Returns true if there are any acks to send to the given contact.
 	 * <p/>
 	 * Read-only.
-	 *
-	 * @param eager True if messages that are not yet due for retransmission
-	 * should be included
 	 */
-	boolean containsAnythingToSend(T txn, ContactId c, long maxLatency,
-			boolean eager) throws DbException;
+	boolean containsAcksToSend(T txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact for the given
@@ -212,6 +207,18 @@ interface Database<T> {
 	 */
 	boolean containsMessage(T txn, MessageId m) throws DbException;
 
+	/**
+	 * Returns true if there are any messages to send to the given
+	 * contact over a transport with the given maximum latency.
+	 * <p/>
+	 * Read-only.
+	 *
+	 * @param eager True if messages that are not yet due for retransmission
+	 * should be included
+	 */
+	boolean containsMessagesToSend(T txn, ContactId c, long maxLatency,
+			boolean eager) throws DbException;
+
 	/**
 	 * Returns true if the database contains the given pending contact.
 	 * <p/>
@@ -580,13 +587,16 @@ interface Database<T> {
 
 	/**
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE
-	 * if no messages are scheduled to be sent.
+	 * message is due to be sent to the given contact over a transport with
+	 * the given latency.
+	 * <p>
+	 * The returned value may be zero if a message is due to be sent
+	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(T txn, ContactId c) throws DbException;
+	long getNextSendTime(T txn, ContactId c, long maxLatency)
+			throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -342,12 +342,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public boolean containsAnythingToSend(Transaction transaction, ContactId c,
-			long maxLatency, boolean eager) throws DbException {
+	public boolean containsAcksToSend(Transaction transaction, ContactId c)
+			throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		return db.containsAnythingToSend(txn, c, maxLatency, eager);
+		return db.containsAcksToSend(txn, c);
 	}
 
 	@Override
@@ -373,6 +373,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.containsIdentity(txn, a);
 	}
 
+	@Override
+	public boolean containsMessagesToSend(Transaction transaction, ContactId c,
+			long maxLatency, boolean eager) throws DbException {
+		T txn = unbox(transaction);
+		if (!db.containsContact(txn, c))
+			throw new NoSuchContactException();
+		return db.containsMessagesToSend(txn, c, maxLatency, eager);
+	}
+
 	@Override
 	public boolean containsPendingContact(Transaction transaction,
 			PendingContactId p) throws DbException {
@@ -805,10 +814,10 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public long getNextSendTime(Transaction transaction, ContactId c)
-			throws DbException {
+	public long getNextSendTime(Transaction transaction, ContactId c,
+			long maxLatency) throws DbException {
 		T txn = unbox(transaction);
-		return db.getNextSendTime(txn, c);
+		return db.getNextSendTime(txn, c, maxLatency);
 	}
 
 	@Override
@@ -1016,7 +1025,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 				db.getGroupVisibility(txn, id).keySet();
 		db.removeGroup(txn, id);
 		transaction.attach(new GroupRemovedEvent(g));
-		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
+		transaction.attach(new GroupVisibilityUpdatedEvent(INVISIBLE,
+				affected));
 	}
 
 	@Override
@@ -1141,7 +1151,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		else if (v == INVISIBLE) db.removeGroupVisibility(txn, c, g);
 		else db.setGroupVisibility(txn, c, g, v == SHARED);
 		List<ContactId> affected = singletonList(c);
-		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
+		transaction.attach(new GroupVisibilityUpdatedEvent(v, affected));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseTypes.java

@@ -3,16 +3,15 @@ package org.briarproject.bramble.db;
 class DatabaseTypes {
 
 	private final String hashType, secretType, binaryType;
-	private final String counterType, stringType, schemaQuery;
+	private final String counterType, stringType;
 
-	DatabaseTypes(String hashType, String secretType, String binaryType,
-			String counterType, String stringType, String schemaQuery) {
+	public DatabaseTypes(String hashType, String secretType, String binaryType,
+			String counterType, String stringType) {
 		this.hashType = hashType;
 		this.secretType = secretType;
 		this.binaryType = binaryType;
 		this.counterType = counterType;
 		this.stringType = stringType;
-		this.schemaQuery = schemaQuery;
 	}
 
 	/**
@@ -32,8 +31,4 @@ class DatabaseTypes {
 		s = s.replaceAll("_STRING", stringType);
 		return s;
 	}
-
-	String getSchemaQuery() {
-		return schemaQuery;
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -41,9 +41,8 @@ class H2Database extends JdbcDatabase {
 	private static final String BINARY_TYPE = "BINARY";
 	private static final String COUNTER_TYPE = "INT NOT NULL AUTO_INCREMENT";
 	private static final String STRING_TYPE = "VARCHAR";
-	private static final String SCHEMA_QUERY = "SHOW TABLES";
 	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
-			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE, SCHEMA_QUERY);
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
 
 	private final DatabaseConfig config;
 	private final String url;

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -41,11 +41,8 @@ class HyperSqlDatabase extends JdbcDatabase {
 	private static final String COUNTER_TYPE =
 			"INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY(START WITH 1)";
 	private static final String STRING_TYPE = "VARCHAR";
-	private static final String SCHEMA_QUERY =
-			"SELECT TABLE_NAME FROM INFORMATION_SCHEMA.SYSTEM_TABLES"
-					+ " WHERE TABLE_TYPE='TABLE'";
 	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
-			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE, SCHEMA_QUERY);
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
 
 	private final DatabaseConfig config;
 	private final String url;

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -405,7 +405,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		boolean compact;
 		Connection txn = startTransaction();
 		try {
-			if (LOG.isLoggable(INFO)) logSchema(txn);
 			if (reopen) {
 				Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
 				wasDirtyOnInitialisation = isDirty(s);
@@ -448,24 +447,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		return wasDirtyOnInitialisation;
 	}
 
-	private void logSchema(Connection txn) throws DbException {
-		Statement s = null;
-		ResultSet rs = null;
-		try {
-			s = txn.createStatement();
-			rs = s.executeQuery(dbTypes.getSchemaQuery());
-			StringBuilder sb = new StringBuilder("Tables:");
-			while (rs.next()) sb.append('\n').append(rs.getString(1));
-			LOG.info(sb.toString());
-			rs.close();
-			s.close();
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(s, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	/**
 	 * Compares the schema version stored in the database with the schema
 	 * version used by the current code and applies any suitable migrations to
@@ -1166,8 +1147,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public boolean containsAnythingToSend(Connection txn, ContactId c,
-			long maxLatency, boolean eager) throws DbException {
+	public boolean containsAcksToSend(Connection txn, ContactId c)
+			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -1179,34 +1160,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			boolean acksToSend = rs.next();
 			rs.close();
 			ps.close();
-			if (acksToSend) return true;
-			if (eager) {
-				sql = "SELECT NULL from statuses"
-						+ " WHERE contactId = ? AND state = ?"
-						+ " AND groupShared = TRUE AND messageShared = TRUE"
-						+ " AND deleted = FALSE AND seen = FALSE";
-				ps = txn.prepareStatement(sql);
-				ps.setInt(1, c.getInt());
-				ps.setInt(2, DELIVERED.getValue());
-			} else {
-				long now = clock.currentTimeMillis();
-				sql = "SELECT NULL FROM statuses"
-						+ " WHERE contactId = ? AND state = ?"
-						+ " AND groupShared = TRUE AND messageShared = TRUE"
-						+ " AND deleted = FALSE AND seen = FALSE"
-						+ " AND (expiry <= ? OR maxLatency IS NULL"
-						+ " OR ? < maxLatency)";
-				ps = txn.prepareStatement(sql);
-				ps.setInt(1, c.getInt());
-				ps.setInt(2, DELIVERED.getValue());
-				ps.setLong(3, now);
-				ps.setLong(4, maxLatency);
-			}
-			rs = ps.executeQuery();
-			boolean messagesToSend = rs.next();
-			rs.close();
-			ps.close();
-			return messagesToSend;
+			return acksToSend;
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
 			tryToClose(ps, LOG, WARNING);
@@ -1326,6 +1280,46 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public boolean containsMessagesToSend(Connection txn, ContactId c,
+			long maxLatency, boolean eager) throws DbException {
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			if (eager) {
+				String sql = "SELECT NULL from statuses"
+						+ " WHERE contactId = ? AND state = ?"
+						+ " AND groupShared = TRUE AND messageShared = TRUE"
+						+ " AND deleted = FALSE AND seen = FALSE";
+				ps = txn.prepareStatement(sql);
+				ps.setInt(1, c.getInt());
+				ps.setInt(2, DELIVERED.getValue());
+			} else {
+				long now = clock.currentTimeMillis();
+				String sql = "SELECT NULL FROM statuses"
+						+ " WHERE contactId = ? AND state = ?"
+						+ " AND groupShared = TRUE AND messageShared = TRUE"
+						+ " AND deleted = FALSE AND seen = FALSE"
+						+ " AND (expiry <= ? OR maxLatency IS NULL"
+						+ " OR ? < maxLatency)";
+				ps = txn.prepareStatement(sql);
+				ps.setInt(1, c.getInt());
+				ps.setInt(2, DELIVERED.getValue());
+				ps.setLong(3, now);
+				ps.setLong(4, maxLatency);
+			}
+			rs = ps.executeQuery();
+			boolean messagesToSend = rs.next();
+			rs.close();
+			ps.close();
+			return messagesToSend;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public boolean containsPendingContact(Connection txn, PendingContactId p)
 			throws DbException {
@@ -2496,12 +2490,28 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public long getNextSendTime(Connection txn, ContactId c)
+	public long getNextSendTime(Connection txn, ContactId c, long maxLatency)
 			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT expiry FROM statuses"
+			// Are any messages sendable immediately?
+			String sql = "SELECT NULL FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE AND seen = FALSE"
+					+ " AND (maxLatency IS NULL OR ? < maxLatency)";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setLong(3, maxLatency);
+			rs = ps.executeQuery();
+			boolean found = rs.next();
+			rs.close();
+			ps.close();
+			if (found) return 0;
+			// When is the earliest expiry time (could be in the past)?
+			sql = "SELECT expiry FROM statuses"
 					+ " WHERE contactId = ? AND state = ?"
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE AND seen = FALSE"

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleManagerImpl.java

@@ -18,7 +18,7 @@ import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
@@ -29,10 +29,12 @@ import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.COMPACTING_DATABASE;
+import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.CREATED;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.MIGRATING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING_SERVICES;
+import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPED;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.ALREADY_RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.CLOCK_ERROR;
@@ -60,12 +62,11 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 	private final List<Service> services;
 	private final List<OpenDatabaseHook> openDatabaseHooks;
 	private final List<ExecutorService> executors;
-	private final Semaphore startStopSemaphore = new Semaphore(1);
 	private final CountDownLatch dbLatch = new CountDownLatch(1);
 	private final CountDownLatch startupLatch = new CountDownLatch(1);
 	private final CountDownLatch shutdownLatch = new CountDownLatch(1);
-
-	private volatile LifecycleState state = STARTING;
+	private final AtomicReference<LifecycleState> state =
+			new AtomicReference<>(CREATED);
 
 	@Inject
 	LifecycleManagerImpl(DatabaseComponent db, EventBus eventBus,
@@ -102,8 +103,8 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 
 	@Override
 	public StartResult startServices(SecretKey dbKey) {
-		if (!startStopSemaphore.tryAcquire()) {
-			LOG.info("Already starting or stopping");
+		if (!state.compareAndSet(CREATED, STARTING)) {
+			LOG.warning("Already running");
 			return ALREADY_RUNNING;
 		}
 		long now = clock.currentTimeMillis();
@@ -135,7 +136,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 			});
 
 			LOG.info("Starting services");
-			state = STARTING_SERVICES;
+			state.set(STARTING_SERVICES);
 			dbLatch.countDown();
 			eventBus.broadcast(new LifecycleEvent(STARTING_SERVICES));
 
@@ -148,7 +149,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 				}
 			}
 
-			state = RUNNING;
+			state.set(RUNNING);
 			startupLatch.countDown();
 			eventBus.broadcast(new LifecycleEvent(RUNNING));
 			return SUCCESS;
@@ -164,63 +165,58 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		} catch (ServiceException e) {
 			logException(LOG, WARNING, e);
 			return SERVICE_ERROR;
-		} finally {
-			startStopSemaphore.release();
 		}
 	}
 
 	@Override
 	public void onDatabaseMigration() {
-		state = MIGRATING_DATABASE;
+		state.set(MIGRATING_DATABASE);
 		eventBus.broadcast(new LifecycleEvent(MIGRATING_DATABASE));
 	}
 
 	@Override
 	public void onDatabaseCompaction() {
-		state = COMPACTING_DATABASE;
+		state.set(COMPACTING_DATABASE);
 		eventBus.broadcast(new LifecycleEvent(COMPACTING_DATABASE));
 	}
 
 	@Override
 	public void stopServices() {
-		try {
-			startStopSemaphore.acquire();
-		} catch (InterruptedException e) {
-			LOG.warning("Interrupted while waiting to stop services");
+		if (!state.compareAndSet(RUNNING, STOPPING)) {
+			LOG.warning("Not running");
 			return;
 		}
-		try {
-			if (state == STOPPING) {
-				LOG.info("Already stopped");
-				return;
-			}
-			LOG.info("Stopping services");
-			state = STOPPING;
-			eventBus.broadcast(new LifecycleEvent(STOPPING));
-			for (Service s : services) {
+		LOG.info("Stopping services");
+		eventBus.broadcast(new LifecycleEvent(STOPPING));
+		for (Service s : services) {
+			try {
 				long start = now();
 				s.stopService();
 				if (LOG.isLoggable(FINE)) {
 					logDuration(LOG, "Stopping service "
 							+ s.getClass().getSimpleName(), start);
 				}
+			} catch (ServiceException e) {
+				logException(LOG, WARNING, e);
 			}
-			for (ExecutorService e : executors) {
-				if (LOG.isLoggable(FINE)) {
-					LOG.fine("Stopping executor "
-							+ e.getClass().getSimpleName());
-				}
-				e.shutdownNow();
+		}
+		for (ExecutorService e : executors) {
+			if (LOG.isLoggable(FINE)) {
+				LOG.fine("Stopping executor "
+						+ e.getClass().getSimpleName());
 			}
+			e.shutdownNow();
+		}
+		try {
 			long start = now();
 			db.close();
 			logDuration(LOG, "Closing database", start);
-			shutdownLatch.countDown();
-		} catch (DbException | ServiceException e) {
+		} catch (DbException e) {
 			logException(LOG, WARNING, e);
-		} finally {
-			startStopSemaphore.release();
 		}
+		state.set(STOPPED);
+		shutdownLatch.countDown();
+		eventBus.broadcast(new LifecycleEvent(STOPPED));
 	}
 
 	@Override
@@ -240,6 +236,6 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 
 	@Override
 	public LifecycleState getLifecycleState() {
-		return state;
+		return state.get();
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ConnectivityChecker.java

@@ -22,10 +22,21 @@ interface ConnectivityChecker {
 	 * the check succeeds. If a check is already running then the observer is
 	 * called when the check succeeds. If a connectivity check has recently
 	 * succeeded then the observer is called immediately.
+	 * <p>
+	 * Observers are removed after being called, or when the checker is
+	 * {@link #destroy() destroyed}.
 	 */
 	void checkConnectivity(MailboxProperties properties,
 			ConnectivityObserver o);
 
+	/**
+	 * Removes an observer that was added via
+	 * {@link #checkConnectivity(MailboxProperties, ConnectivityObserver)}. If
+	 * there are no remaining observers and a connectivity check is running
+	 * then the check will be cancelled.
+	 */
+	void removeObserver(ConnectivityObserver o);
+
 	interface ConnectivityObserver {
 		void onConnectivityCheckSucceeded();
 	}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ConnectivityCheckerImpl.java

@@ -80,8 +80,7 @@ abstract class ConnectivityCheckerImpl implements ConnectivityChecker {
 						> CONNECTIVITY_CHECK_FRESHNESS_MS) {
 					// The last connectivity check is stale, start a new one
 					connectivityObservers.add(o);
-					ApiCall task =
-							createConnectivityCheckTask(properties);
+					ApiCall task = createConnectivityCheckTask(properties);
 					connectivityCheck = mailboxApiCaller.retryWithBackoff(task);
 				} else {
 					// The last connectivity check is fresh
@@ -108,4 +107,16 @@ abstract class ConnectivityCheckerImpl implements ConnectivityChecker {
 			o.onConnectivityCheckSucceeded();
 		}
 	}
+
+	@Override
+	public void removeObserver(ConnectivityObserver o) {
+		synchronized (lock) {
+			if (destroyed) return;
+			connectivityObservers.remove(o);
+			if (connectivityObservers.isEmpty() && connectivityCheck != null) {
+				connectivityCheck.cancel();
+				connectivityCheck = null;
+			}
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxClient.java

@@ -0,0 +1,120 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Logger.getLogger;
+
+@ThreadSafe
+@NotNullByDefault
+class ContactMailboxClient implements MailboxClient {
+
+	private static final Logger LOG =
+			getLogger(ContactMailboxClient.class.getName());
+
+	private final MailboxWorkerFactory workerFactory;
+	private final ConnectivityChecker connectivityChecker;
+	private final TorReachabilityMonitor reachabilityMonitor;
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	@Nullable
+	private MailboxWorker uploadWorker = null, downloadWorker = null;
+
+	ContactMailboxClient(MailboxWorkerFactory workerFactory,
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor) {
+		this.workerFactory = workerFactory;
+		this.connectivityChecker = connectivityChecker;
+		this.reachabilityMonitor = reachabilityMonitor;
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		// Nothing to do until contact is assigned
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		MailboxWorker uploadWorker, downloadWorker;
+		synchronized (lock) {
+			uploadWorker = this.uploadWorker;
+			this.uploadWorker = null;
+			downloadWorker = this.downloadWorker;
+			this.downloadWorker = null;
+		}
+		if (uploadWorker != null) uploadWorker.destroy();
+		if (downloadWorker != null) downloadWorker.destroy();
+	}
+
+	@Override
+	public void assignContactForUpload(ContactId contactId,
+			MailboxProperties properties, MailboxFolderId folderId) {
+		LOG.info("Contact assigned for upload");
+		if (properties.isOwner()) throw new IllegalArgumentException();
+		// For a contact's mailbox we should always be uploading to the outbox
+		// assigned to us by the contact
+		if (!folderId.equals(properties.getOutboxId())) {
+			throw new IllegalArgumentException();
+		}
+		MailboxWorker uploadWorker = workerFactory.createUploadWorker(
+				connectivityChecker, properties, folderId, contactId);
+		synchronized (lock) {
+			if (this.uploadWorker != null) throw new IllegalStateException();
+			this.uploadWorker = uploadWorker;
+		}
+		uploadWorker.start();
+	}
+
+	@Override
+	public void deassignContactForUpload(ContactId contactId) {
+		LOG.info("Contact deassigned for upload");
+		MailboxWorker uploadWorker;
+		synchronized (lock) {
+			uploadWorker = this.uploadWorker;
+			this.uploadWorker = null;
+		}
+		if (uploadWorker != null) uploadWorker.destroy();
+	}
+
+	@Override
+	public void assignContactForDownload(ContactId contactId,
+			MailboxProperties properties, MailboxFolderId folderId) {
+		LOG.info("Contact assigned for download");
+		if (properties.isOwner()) throw new IllegalArgumentException();
+		// For a contact's mailbox we should always be downloading from the
+		// inbox assigned to us by the contact
+		if (!folderId.equals(properties.getInboxId())) {
+			throw new IllegalArgumentException();
+		}
+		MailboxWorker downloadWorker =
+				workerFactory.createDownloadWorkerForContactMailbox(
+						connectivityChecker, reachabilityMonitor, properties);
+		synchronized (lock) {
+			if (this.downloadWorker != null) throw new IllegalStateException();
+			this.downloadWorker = downloadWorker;
+		}
+		downloadWorker.start();
+	}
+
+	@Override
+	public void deassignContactForDownload(ContactId contactId) {
+		LOG.info("Contact deassigned for download");
+		MailboxWorker downloadWorker;
+		synchronized (lock) {
+			downloadWorker = this.downloadWorker;
+			this.downloadWorker = null;
+		}
+		if (downloadWorker != null) downloadWorker.destroy();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxConnectivityChecker.java

@@ -5,8 +5,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 
-import java.io.IOException;
-
 import javax.annotation.concurrent.ThreadSafe;
 
 @ThreadSafe
@@ -24,16 +22,11 @@ class ContactMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 	@Override
 	ApiCall createConnectivityCheckTask(MailboxProperties properties) {
 		if (properties.isOwner()) throw new IllegalArgumentException();
-		return new SimpleApiCall() {
-			@Override
-			void tryToCallApi() throws IOException, ApiException {
-				if (!mailboxApi.checkStatus(properties)) {
-					throw new ApiException();
-				}
-				// Call the observers and cache the result
-				onConnectivityCheckSucceeded(clock.currentTimeMillis());
-			}
-		};
+		return new SimpleApiCall(() -> {
+			if (!mailboxApi.checkStatus(properties)) throw new ApiException();
+			// Call the observers and cache the result
+			onConnectivityCheckSucceeded(clock.currentTimeMillis());
+		});
 	}
 
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxDownloadWorker.java

@@ -0,0 +1,65 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+
+import java.io.IOException;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.Collections.emptyList;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+
+@ThreadSafe
+@NotNullByDefault
+class ContactMailboxDownloadWorker extends MailboxDownloadWorker {
+
+	ContactMailboxDownloadWorker(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor torReachabilityMonitor,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxProperties mailboxProperties) {
+		super(connectivityChecker, torReachabilityMonitor, mailboxApiCaller,
+				mailboxApi, mailboxFileManager, mailboxProperties);
+		if (mailboxProperties.isOwner()) throw new IllegalArgumentException();
+	}
+
+	@Override
+	protected ApiCall createApiCallForDownloadCycle() {
+		return new SimpleApiCall(this::apiCallListInbox);
+	}
+
+	private void apiCallListInbox() throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		LOG.info("Listing inbox");
+		MailboxFolderId folderId =
+				requireNonNull(mailboxProperties.getInboxId());
+		List<MailboxFile> files;
+		try {
+			files = mailboxApi.getFiles(mailboxProperties, folderId);
+		} catch (TolerableFailureException e) {
+			LOG.warning("Inbox folder does not exist");
+			files = emptyList();
+		}
+		if (files.isEmpty()) {
+			onDownloadCycleFinished();
+		} else {
+			Queue<FolderFile> queue = new LinkedList<>();
+			for (MailboxFile file : files) {
+				queue.add(new FolderFile(folderId, file.name));
+			}
+			downloadNextFile(queue);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApi.java

@@ -91,9 +91,13 @@ interface MailboxApi {
 	 * Used by owner and contacts to list their files to retrieve.
 	 * <p>
 	 * Returns 200 OK with the list of files in JSON.
+	 *
+	 * @throws TolerableFailureException if response code is 404 (folder does
+	 * not exist or client is not authorised to download from it)
 	 */
 	List<MailboxFile> getFiles(MailboxProperties properties,
-			MailboxFolderId folderId) throws IOException, ApiException;
+			MailboxFolderId folderId)
+			throws IOException, ApiException, TolerableFailureException;
 
 	/**
 	 * Used by owner and contacts to retrieve a file.
@@ -102,17 +106,22 @@ interface MailboxApi {
 	 * in the response body.
 	 *
 	 * @param file the empty file the response bytes will be written into.
+	 * @throws TolerableFailureException if response code is 404 (folder does
+	 * not exist, client is not authorised to download from folder, or file
+	 * does not exist)
 	 */
 	void getFile(MailboxProperties properties, MailboxFolderId folderId,
-			MailboxFileId fileId, File file) throws IOException, ApiException;
+			MailboxFileId fileId, File file)
+			throws IOException, ApiException, TolerableFailureException;
 
 	/**
 	 * Used by owner and contacts to delete files.
 	 * <p>
 	 * Returns 200 OK (no exception) if deletion was successful.
 	 *
-	 * @throws TolerableFailureException on 404 response,
-	 * because file was most likely deleted already.
+	 * @throws TolerableFailureException if response code is 404 (folder does
+	 * not exist, client is not authorised to download from folder, or file
+	 * does not exist)
 	 */
 	void deleteFile(MailboxProperties properties, MailboxFolderId folderId,
 			MailboxFileId fileId)

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApiCaller.java

@@ -24,6 +24,8 @@ interface MailboxApiCaller {
 	 * Asynchronously calls the given API call on the {@link IoExecutor},
 	 * automatically retrying at increasing intervals until the API call
 	 * returns false or retries are cancelled.
+	 * <p>
+	 * This method is safe to call while holding a lock.
 	 *
 	 * @return A {@link Cancellable} that can be used to cancel any future
 	 * retries.

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApiImpl.java

@@ -42,18 +42,22 @@ import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 @NotNullByDefault
 class MailboxApiImpl implements MailboxApi {
 
-	private final WeakSingletonProvider<OkHttpClient> httpClientProvider;
-	private final JsonMapper mapper = JsonMapper.builder()
-			.enable(BLOCK_UNSAFE_POLYMORPHIC_BASE_TYPES)
-			.build();
 	private static final MediaType JSON =
 			requireNonNull(MediaType.parse("application/json; charset=utf-8"));
 	private static final MediaType FILE =
 			requireNonNull(MediaType.parse("application/octet-stream"));
 
+	private final WeakSingletonProvider<OkHttpClient> httpClientProvider;
+	private final JsonMapper mapper = JsonMapper.builder()
+			.enable(BLOCK_UNSAFE_POLYMORPHIC_BASE_TYPES)
+			.build();
+	private final UrlConverter urlConverter;
+
 	@Inject
-	MailboxApiImpl(WeakSingletonProvider<OkHttpClient> httpClientProvider) {
+	MailboxApiImpl(WeakSingletonProvider<OkHttpClient> httpClientProvider,
+			UrlConverter urlConverter) {
 		this.httpClientProvider = httpClientProvider;
+		this.urlConverter = urlConverter;
 	}
 
 	@Override
@@ -78,7 +82,7 @@ class MailboxApiImpl implements MailboxApi {
 			throws IOException, ApiException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(properties.getBaseUrl() + "/setup")
+				.url(getBaseUrl(properties) + "/setup")
 				.put(EMPTY_REQUEST)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -93,7 +97,7 @@ class MailboxApiImpl implements MailboxApi {
 			if (tokenNode == null) {
 				throw new ApiException();
 			}
-			return new MailboxProperties(properties.getBaseUrl(),
+			return new MailboxProperties(properties.getOnion(),
 					MailboxAuthToken.fromString(tokenNode.textValue()),
 					parseServerSupports(node));
 		} catch (JacksonException | InvalidMailboxIdException e) {
@@ -137,7 +141,7 @@ class MailboxApiImpl implements MailboxApi {
 			throws IOException, ApiException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(properties.getBaseUrl() + "/")
+				.url(getBaseUrl(properties) + "/")
 				.delete()
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -162,7 +166,7 @@ class MailboxApiImpl implements MailboxApi {
 	public void deleteContact(MailboxProperties properties, ContactId contactId)
 			throws IOException, ApiException, TolerableFailureException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
-		String url = properties.getBaseUrl() + "/contacts/" +
+		String url = getBaseUrl(properties) + "/contacts/" +
 				contactId.getInt();
 		Request request = getRequestBuilder(properties.getAuthToken())
 				.delete()
@@ -212,9 +216,11 @@ class MailboxApiImpl implements MailboxApi {
 
 	@Override
 	public List<MailboxFile> getFiles(MailboxProperties properties,
-			MailboxFolderId folderId) throws IOException, ApiException {
+			MailboxFolderId folderId)
+			throws IOException, ApiException, TolerableFailureException {
 		String path = "/files/" + folderId;
 		Response response = sendGetRequest(properties, path);
+		if (response.code() == 404) throw new TolerableFailureException();
 		if (response.code() != 200) throw new ApiException();
 
 		ResponseBody body = response.body();
@@ -248,9 +254,11 @@ class MailboxApiImpl implements MailboxApi {
 
 	@Override
 	public void getFile(MailboxProperties properties, MailboxFolderId folderId,
-			MailboxFileId fileId, File file) throws IOException, ApiException {
+			MailboxFileId fileId, File file)
+			throws IOException, ApiException, TolerableFailureException {
 		String path = "/files/" + folderId + "/" + fileId;
 		Response response = sendGetRequest(properties, path);
+		if (response.code() == 404) throw new TolerableFailureException();
 		if (response.code() != 200) throw new ApiException();
 
 		ResponseBody body = response.body();
@@ -266,7 +274,7 @@ class MailboxApiImpl implements MailboxApi {
 		String path = "/files/" + folderId + "/" + fileId;
 		Request request = getRequestBuilder(properties.getAuthToken())
 				.delete()
-				.url(properties.getBaseUrl() + path)
+				.url(getBaseUrl(properties) + path)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
 		Response response = client.newCall(request).execute();
@@ -308,7 +316,7 @@ class MailboxApiImpl implements MailboxApi {
 	private Response sendGetRequest(MailboxProperties properties, String path)
 			throws IOException {
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(properties.getBaseUrl() + path)
+				.url(getBaseUrl(properties) + path)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
 		return client.newCall(request).execute();
@@ -317,7 +325,7 @@ class MailboxApiImpl implements MailboxApi {
 	private Response sendPostRequest(MailboxProperties properties, String path,
 			RequestBody body) throws IOException {
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(properties.getBaseUrl() + path)
+				.url(getBaseUrl(properties) + path)
 				.post(body)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -339,4 +347,7 @@ class MailboxApiImpl implements MailboxApi {
 		return (ArrayNode) arrayNode;
 	}
 
+	private String getBaseUrl(MailboxProperties properties) {
+		return urlConverter.convertOnionToBaseUrl(properties.getOnion());
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClient.java

@@ -0,0 +1,55 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+@ThreadSafe
+@NotNullByDefault
+interface MailboxClient {
+
+	/**
+	 * Asynchronously starts the client.
+	 */
+	void start();
+
+	/**
+	 * Destroys the client and its workers, cancelling any pending tasks or
+	 * retries.
+	 */
+	void destroy();
+
+	/**
+	 * Assigns a contact to the client for upload.
+	 *
+	 * @param properties Properties for communicating with the mailbox
+	 * managed by this client.
+	 * @param folderId The ID of the folder to which files will be uploaded.
+	 */
+	void assignContactForUpload(ContactId c, MailboxProperties properties,
+			MailboxFolderId folderId);
+
+	/**
+	 * Deassigns a contact from the client for upload.
+	 */
+	void deassignContactForUpload(ContactId c);
+
+	/**
+	 * Assigns a contact to the client for download.
+	 *
+	 * @param properties Properties for communicating with the mailbox
+	 * managed by this client.
+	 * @param folderId The ID of the folder from which files will be
+	 * downloaded.
+	 */
+	void assignContactForDownload(ContactId c, MailboxProperties properties,
+			MailboxFolderId folderId);
+
+	/**
+	 * Deassigns a contact from the client for download.
+	 */
+	void deassignContactForDownload(ContactId c);
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxDownloadWorker.java

@@ -0,0 +1,250 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.mailbox.MailboxFileId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+import org.briarproject.bramble.mailbox.TorReachabilityMonitor.TorReachabilityObserver;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Queue;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Logger.getLogger;
+
+@ThreadSafe
+@NotNullByDefault
+abstract class MailboxDownloadWorker implements MailboxWorker,
+		ConnectivityObserver, TorReachabilityObserver {
+
+	/**
+	 * When the worker is started it waits for a connectivity check, then
+	 * starts its first download cycle: checking for files to download,
+	 * downloading and deleting the files, and checking again until all files
+	 * have been downloaded and deleted.
+	 * <p>
+	 * The worker then waits for our Tor hidden service to be reachable before
+	 * starting its second download cycle. This ensures that if a contact
+	 * tried and failed to connect to our hidden service before it was
+	 * reachable, and therefore uploaded a file to the mailbox instead, we'll
+	 * find the file in the second download cycle.
+	 */
+	protected enum State {
+		CREATED,
+		CONNECTIVITY_CHECK,
+		DOWNLOAD_CYCLE_1,
+		WAITING_FOR_TOR,
+		DOWNLOAD_CYCLE_2,
+		FINISHED,
+		DESTROYED
+	}
+
+	protected static final Logger LOG =
+			getLogger(MailboxDownloadWorker.class.getName());
+
+	private final ConnectivityChecker connectivityChecker;
+	private final TorReachabilityMonitor torReachabilityMonitor;
+	protected final MailboxApiCaller mailboxApiCaller;
+	protected final MailboxApi mailboxApi;
+	private final MailboxFileManager mailboxFileManager;
+	protected final MailboxProperties mailboxProperties;
+	protected final Object lock = new Object();
+
+	@GuardedBy("lock")
+	protected State state = State.CREATED;
+
+	@GuardedBy("lock")
+	@Nullable
+	protected Cancellable apiCall = null;
+
+	/**
+	 * Creates the API call that starts the worker's download cycle.
+	 */
+	protected abstract ApiCall createApiCallForDownloadCycle();
+
+	MailboxDownloadWorker(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor torReachabilityMonitor,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxProperties mailboxProperties) {
+		this.connectivityChecker = connectivityChecker;
+		this.torReachabilityMonitor = torReachabilityMonitor;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxFileManager = mailboxFileManager;
+		this.mailboxProperties = mailboxProperties;
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		synchronized (lock) {
+			// Don't allow the worker to be reused
+			if (state != State.CREATED) return;
+			state = State.CONNECTIVITY_CHECK;
+		}
+		// Avoid leaking observer in case destroy() is called concurrently
+		// before observer is added
+		connectivityChecker.checkConnectivity(mailboxProperties, this);
+		boolean destroyed;
+		synchronized (lock) {
+			destroyed = state == State.DESTROYED;
+		}
+		if (destroyed) connectivityChecker.removeObserver(this);
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		Cancellable apiCall;
+		synchronized (lock) {
+			state = State.DESTROYED;
+			apiCall = this.apiCall;
+			this.apiCall = null;
+		}
+		if (apiCall != null) apiCall.cancel();
+		connectivityChecker.removeObserver(this);
+		torReachabilityMonitor.removeObserver(this);
+	}
+
+	@Override
+	public void onConnectivityCheckSucceeded() {
+		LOG.info("Connectivity check succeeded");
+		synchronized (lock) {
+			if (state != State.CONNECTIVITY_CHECK) return;
+			state = State.DOWNLOAD_CYCLE_1;
+			// Start first download cycle
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					createApiCallForDownloadCycle());
+		}
+	}
+
+	void onDownloadCycleFinished() {
+		boolean addObserver = false;
+		synchronized (lock) {
+			if (state == State.DOWNLOAD_CYCLE_1) {
+				LOG.info("First download cycle finished");
+				state = State.WAITING_FOR_TOR;
+				apiCall = null;
+				addObserver = true;
+			} else if (state == State.DOWNLOAD_CYCLE_2) {
+				LOG.info("Second download cycle finished");
+				state = State.FINISHED;
+				apiCall = null;
+			}
+		}
+		if (addObserver) {
+			// Avoid leaking observer in case destroy() is called concurrently
+			// before observer is added
+			torReachabilityMonitor.addOneShotObserver(this);
+			boolean destroyed;
+			synchronized (lock) {
+				destroyed = state == State.DESTROYED;
+			}
+			if (destroyed) torReachabilityMonitor.removeObserver(this);
+		}
+	}
+
+	void downloadNextFile(Queue<FolderFile> queue) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+			if (queue.isEmpty()) {
+				// Check for files again, as new files may have arrived while
+				// we were downloading
+				apiCall = mailboxApiCaller.retryWithBackoff(
+						createApiCallForDownloadCycle());
+			} else {
+				FolderFile file = queue.remove();
+				apiCall = mailboxApiCaller.retryWithBackoff(
+						new SimpleApiCall(() ->
+								apiCallDownloadFile(file, queue)));
+			}
+		}
+	}
+
+	private void apiCallDownloadFile(FolderFile file, Queue<FolderFile> queue)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		LOG.info("Downloading file");
+		File tempFile = mailboxFileManager.createTempFileForDownload();
+		try {
+			mailboxApi.getFile(mailboxProperties, file.folderId, file.fileId,
+					tempFile);
+		} catch (IOException | ApiException e) {
+			if (!tempFile.delete()) {
+				LOG.warning("Failed to delete temporary file");
+			}
+			throw e;
+		} catch (TolerableFailureException e) {
+			// File not found - continue to the next file
+			LOG.warning("File does not exist");
+			if (!tempFile.delete()) {
+				LOG.warning("Failed to delete temporary file");
+			}
+			downloadNextFile(queue);
+			return;
+		}
+		mailboxFileManager.handleDownloadedFile(tempFile);
+		deleteFile(file, queue);
+	}
+
+	private void deleteFile(FolderFile file, Queue<FolderFile> queue) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(() -> apiCallDeleteFile(file, queue)));
+		}
+	}
+
+	private void apiCallDeleteFile(FolderFile file, Queue<FolderFile> queue)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		try {
+			mailboxApi.deleteFile(mailboxProperties, file.folderId,
+					file.fileId);
+		} catch (TolerableFailureException e) {
+			// File not found - continue to the next file
+			LOG.warning("File does not exist");
+		}
+		downloadNextFile(queue);
+	}
+
+	@Override
+	public void onTorReachable() {
+		LOG.info("Our Tor hidden service is reachable");
+		synchronized (lock) {
+			if (state != State.WAITING_FOR_TOR) return;
+			state = State.DOWNLOAD_CYCLE_2;
+			// Start second download cycle
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					createApiCallForDownloadCycle());
+		}
+	}
+
+	// Package access for testing
+	static class FolderFile {
+
+		final MailboxFolderId folderId;
+		final MailboxFileId fileId;
+
+		FolderFile(MailboxFolderId folderId, MailboxFileId fileId) {
+			this.folderId = folderId;
+			this.fileId = fileId;
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManager.java

@@ -1,6 +1,8 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
@@ -16,6 +18,14 @@ interface MailboxFileManager {
 	 */
 	File createTempFileForDownload() throws IOException;
 
+	/**
+	 * Creates a file to be uploaded to the given contact and writes any
+	 * waiting data to the file. The IDs of any messages sent or acked will
+	 * be added to the given {@link OutgoingSessionRecord}.
+	 */
+	File createAndWriteTempFileForUpload(ContactId contactId,
+			OutgoingSessionRecord sessionRecord) throws IOException;
+
 	/**
 	 * Handles a file that has been downloaded. The file should be created
 	 * with {@link #createTempFileForDownload()}.

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManagerImpl.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -10,13 +11,18 @@ import org.briarproject.bramble.api.mailbox.MailboxDirectory;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
@@ -30,6 +36,7 @@ import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleS
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.plugin.file.FileConstants.PROP_PATH;
+import static org.briarproject.bramble.util.IoUtils.delete;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @ThreadSafe
@@ -41,6 +48,7 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	// Package access for testing
 	static final String DOWNLOAD_DIR_NAME = "downloads";
+	static final String UPLOAD_DIR_NAME = "uploads";
 
 	private final Executor ioExecutor;
 	private final PluginManager pluginManager;
@@ -67,14 +75,44 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public File createTempFileForDownload() throws IOException {
+		return createTempFile(DOWNLOAD_DIR_NAME);
+	}
+
+	@Override
+	public File createAndWriteTempFileForUpload(ContactId contactId,
+			OutgoingSessionRecord sessionRecord) throws IOException {
+		File f = createTempFile(UPLOAD_DIR_NAME);
+		// We shouldn't reach this point until the plugin has been started
+		SimplexPlugin plugin =
+				(SimplexPlugin) requireNonNull(pluginManager.getPlugin(ID));
+		TransportProperties p = new TransportProperties();
+		p.put(PROP_PATH, f.getAbsolutePath());
+		TransportConnectionWriter writer = plugin.createWriter(p);
+		if (writer == null) {
+			delete(f);
+			throw new IOException();
+		}
+		MailboxFileWriter decorated = new MailboxFileWriter(writer);
+		LOG.info("Writing file for upload");
+		connectionManager.manageOutgoingConnection(contactId, ID, decorated,
+				sessionRecord);
+		if (decorated.awaitDisposal()) {
+			// An exception was thrown during the session - delete the file
+			delete(f);
+			throw new IOException();
+		}
+		return f;
+	}
+
+	private File createTempFile(String dirName) throws IOException {
 		// Wait for orphaned files to be handled before creating new files
 		try {
 			orphanLatch.await();
 		} catch (InterruptedException e) {
 			throw new IOException(e);
 		}
-		File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
-		return File.createTempFile("mailbox", ".tmp", downloadDir);
+		File dir = createDirectoryIfNeeded(dirName);
+		return File.createTempFile("mailbox", ".tmp", dir);
 	}
 
 	private File createDirectoryIfNeeded(String name) throws IOException {
@@ -116,6 +154,8 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
+		// Wait for the transport to become active before handling orphaned
+		// files so that we can get the plugin from the plugin manager
 		if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			if (t.getTransportId().equals(ID)) {
@@ -127,17 +167,25 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	/**
 	 * This method is called at startup, as soon as the plugin is started, to
-	 * handle any files that were left in the download directory at the last
-	 * shutdown.
+	 * delete any files that were left in the upload directory at the last
+	 * shutdown and handle any files that were left in the download directory.
 	 */
 	@IoExecutor
 	private void handleOrphanedFiles() {
 		try {
+			File uploadDir = createDirectoryIfNeeded(UPLOAD_DIR_NAME);
+			File[] orphanedUploads = uploadDir.listFiles();
+			if (orphanedUploads != null) {
+				for (File f : orphanedUploads) delete(f);
+			}
 			File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
-			File[] orphans = downloadDir.listFiles();
-			// Now that we've got the list of orphans, new files can be created
+			File[] orphanedDownloads = downloadDir.listFiles();
+			// Now that we've got the list of orphaned downloads, new files
+			// can be created in the download directory
 			orphanLatch.countDown();
-			if (orphans != null) for (File f : orphans) handleDownloadedFile(f);
+			if (orphanedDownloads != null) {
+				for (File f : orphanedDownloads) handleDownloadedFile(f);
+			}
 		} catch (IOException e) {
 			logException(LOG, WARNING, e);
 		}
@@ -165,9 +213,58 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 			delegate.dispose(exception, recognised);
 			if (isHandlingComplete(exception, recognised)) {
 				LOG.info("Deleting downloaded file");
-				if (!file.delete()) {
-					LOG.warning("Failed to delete downloaded file");
-				}
+				delete(file);
+			}
+		}
+	}
+
+	private static class MailboxFileWriter
+			implements TransportConnectionWriter {
+
+		private final TransportConnectionWriter delegate;
+		private final BlockingQueue<Boolean> disposalResult =
+				new ArrayBlockingQueue<>(1);
+
+		private MailboxFileWriter(TransportConnectionWriter delegate) {
+			this.delegate = delegate;
+		}
+
+		@Override
+		public long getMaxLatency() {
+			return delegate.getMaxLatency();
+		}
+
+		@Override
+		public int getMaxIdleTime() {
+			return delegate.getMaxIdleTime();
+		}
+
+		@Override
+		public boolean isLossyAndCheap() {
+			return delegate.isLossyAndCheap();
+		}
+
+		@Override
+		public OutputStream getOutputStream() throws IOException {
+			return delegate.getOutputStream();
+		}
+
+		@Override
+		public void dispose(boolean exception) throws IOException {
+			delegate.dispose(exception);
+			disposalResult.add(exception);
+		}
+
+		/**
+		 * Waits for the delegate to be disposed and returns true if an
+		 * exception occurred.
+		 */
+		private boolean awaitDisposal() {
+			try {
+				return disposalResult.take();
+			} catch (InterruptedException e) {
+				LOG.info("Interrupted while waiting for disposal");
+				return true;
 			}
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxManagerImpl.java

@@ -9,10 +9,12 @@ import org.briarproject.bramble.api.mailbox.MailboxPairingTask;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -98,34 +100,35 @@ class MailboxManagerImpl implements MailboxManager {
 
 	@Override
 	public boolean checkConnection() {
-		boolean success;
+		List<MailboxVersion> versions = null;
 		try {
 			MailboxProperties props = db.transactionWithNullableResult(true,
 					mailboxSettingsManager::getOwnMailboxProperties);
 			if (props == null) throw new DbException();
-			success = api.checkStatus(props);
+			versions = api.getServerSupports(props);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 			// we don't treat this is a failure to record
 			return false;
 		} catch (IOException | MailboxApi.ApiException e) {
 			// we record this as a failure
-			success = false;
 			logException(LOG, WARNING, e);
 		}
 		try {
-			recordCheckResult(success);
+			recordCheckResult(versions);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 		}
-		return success;
+		return versions != null;
 	}
 
-	private void recordCheckResult(boolean success) throws DbException {
+	private void recordCheckResult(@Nullable List<MailboxVersion> versions)
+			throws DbException {
 		long now = clock.currentTimeMillis();
 		db.transaction(false, txn -> {
-			if (success) {
-				mailboxSettingsManager.recordSuccessfulConnection(txn, now);
+			if (versions != null) {
+				mailboxSettingsManager
+						.recordSuccessfulConnection(txn, now, versions);
 			} else {
 				mailboxSettingsManager.recordFailedConnectionAttempt(txn, now);
 			}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxModule.java

@@ -52,13 +52,19 @@ public class MailboxModule {
 	}
 
 	@Provides
+	@Singleton
 	MailboxSettingsManager provideMailboxSettingsManager(
 			MailboxSettingsManagerImpl mailboxSettingsManager) {
 		return mailboxSettingsManager;
 	}
 
 	@Provides
-	MailboxApi providesMailboxApi(MailboxApiImpl mailboxApi) {
+	UrlConverter provideUrlConverter(UrlConverterImpl urlConverter) {
+		return urlConverter;
+	}
+
+	@Provides
+	MailboxApi provideMailboxApi(MailboxApiImpl mailboxApi) {
 		return mailboxApi;
 	}
 
@@ -114,4 +120,10 @@ public class MailboxModule {
 		}
 		return mailboxFileManager;
 	}
+
+	@Provides
+	MailboxWorkerFactory provideMailboxWorkerFactory(
+			MailboxWorkerFactoryImpl mailboxWorkerFactory) {
+		return mailboxWorkerFactory;
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImpl.java

@@ -177,10 +177,9 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 		LOG.info("QR code is valid");
 		byte[] onionPubKey = Arrays.copyOfRange(bytes, 1, 33);
 		String onion = crypto.encodeOnion(onionPubKey);
-		String baseUrl = "http://" + onion + ".onion"; // TODO
 		byte[] tokenBytes = Arrays.copyOfRange(bytes, 33, 65);
 		MailboxAuthToken setupToken = new MailboxAuthToken(tokenBytes);
-		return new MailboxProperties(baseUrl, setupToken, new ArrayList<>());
+		return new MailboxProperties(onion, setupToken, new ArrayList<>());
 	}
 
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImpl.java

@@ -20,13 +20,13 @@ import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.Immutable;
+import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
-@Immutable
+@ThreadSafe
 @NotNullByDefault
 class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 
@@ -74,16 +74,10 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 	public void setOwnMailboxProperties(Transaction txn, MailboxProperties p)
 			throws DbException {
 		Settings s = new Settings();
-		s.put(SETTINGS_KEY_ONION, p.getBaseUrl());
+		s.put(SETTINGS_KEY_ONION, p.getOnion());
 		s.put(SETTINGS_KEY_TOKEN, p.getAuthToken().toString());
 		List<MailboxVersion> serverSupports = p.getServerSupports();
-		int[] ints = new int[serverSupports.size() * 2];
-		int i = 0;
-		for (MailboxVersion v : serverSupports) {
-			ints[i++] = v.getMajor();
-			ints[i++] = v.getMinor();
-		}
-		s.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, ints);
+		encodeServerSupports(serverSupports, s);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
 		for (MailboxHook hook : hooks) {
 			hook.mailboxPaired(txn, p.getOnion(), p.getServerSupports());
@@ -121,14 +115,30 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 	@Override
 	public void recordSuccessfulConnection(Transaction txn, long now)
 			throws DbException {
-		Settings oldSettings =
-				settingsManager.getSettings(txn, SETTINGS_NAMESPACE);
+		recordSuccessfulConnection(txn, now, null);
+	}
+
+	@Override
+	public void recordSuccessfulConnection(Transaction txn, long now,
+			@Nullable List<MailboxVersion> versions) throws DbException {
 		Settings s = new Settings();
+		// fetch version that the server supports first
+		List<MailboxVersion> serverSupports;
+		if (versions == null) {
+			Settings oldSettings =
+					settingsManager.getSettings(txn, SETTINGS_NAMESPACE);
+			serverSupports = parseServerSupports(oldSettings);
+		} else {
+			serverSupports = versions;
+			// store new versions
+			encodeServerSupports(serverSupports, s);
+		}
+		// now record the successful connection
 		s.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
 		s.putLong(SETTINGS_KEY_LAST_SUCCESS, now);
 		s.putInt(SETTINGS_KEY_ATTEMPTS, 0);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
-		List<MailboxVersion> serverSupports = parseServerSupports(oldSettings);
+		// broadcast status event
 		MailboxStatus status = new MailboxStatus(now, now, 0, serverSupports);
 		txn.attach(new OwnMailboxConnectionStatusEvent(status));
 	}
@@ -171,6 +181,17 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		return filename;
 	}
 
+	private void encodeServerSupports(List<MailboxVersion> serverSupports,
+			Settings s) {
+		int[] ints = new int[serverSupports.size() * 2];
+		int i = 0;
+		for (MailboxVersion v : serverSupports) {
+			ints[i++] = v.getMajor();
+			ints[i++] = v.getMinor();
+		}
+		s.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, ints);
+	}
+
 	private List<MailboxVersion> parseServerSupports(Settings s)
 			throws DbException {
 		if (!s.containsKey(SETTINGS_KEY_SERVER_SUPPORTS)) return emptyList();

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxUpdateManagerImpl.java

@@ -242,8 +242,7 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 	private void createAndSendUpdateWithMailbox(Transaction txn, Contact c,
 			List<MailboxVersion> serverSupports, String ownOnion)
 			throws DbException {
-		String baseUrl = "http://" + ownOnion + ".onion"; // TODO
-		MailboxProperties properties = new MailboxProperties(baseUrl,
+		MailboxProperties properties = new MailboxProperties(ownOnion,
 				new MailboxAuthToken(crypto.generateUniqueId().getBytes()),
 				serverSupports,
 				new MailboxFolderId(crypto.generateUniqueId().getBytes()),

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxUploadWorker.java

@@ -0,0 +1,394 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventExecutor;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
+import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
+import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
+import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
+import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
+import static org.briarproject.bramble.util.IoUtils.delete;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@ThreadSafe
+@NotNullByDefault
+class MailboxUploadWorker implements MailboxWorker, ConnectivityObserver,
+		EventListener {
+
+	/**
+	 * When the worker is started it checks for data to send. If data is ready
+	 * to send, the worker waits for a connectivity check, then writes and
+	 * uploads a file and checks again for data to send.
+	 * <p>
+	 * If data is due to be sent at some time in the future, the worker
+	 * schedules a wakeup for that time and also listens for events indicating
+	 * that new data may be ready to send.
+	 * <p>
+	 * If there's no data to send, the worker listens for events indicating
+	 * that new data may be ready to send.
+	 */
+	private enum State {
+		CREATED,
+		CHECKING_FOR_DATA,
+		WAITING_FOR_DATA,
+		CONNECTIVITY_CHECK,
+		WRITING_UPLOADING,
+		DESTROYED
+	}
+
+	private static final Logger LOG =
+			getLogger(MailboxUploadWorker.class.getName());
+
+	/**
+	 * When we're waiting for data to send and an event indicates that new data
+	 * may have become available, wait this long before checking the DB. This
+	 * should help to avoid creating lots of small files when several acks or
+	 * messages become available to send in a short period (eg when reading a
+	 * file downloaded from a mailbox).
+	 * <p>
+	 * Package access for testing.
+	 */
+	static final long CHECK_DELAY_MS = 5_000;
+
+	/**
+	 * How long to wait before retrying when an exception occurs while writing
+	 * a file.
+	 * <p>
+	 * Package access for testing.
+	 */
+	static final long RETRY_DELAY_MS = MINUTES.toMillis(1);
+
+	private final Executor ioExecutor;
+	private final DatabaseComponent db;
+	private final Clock clock;
+	private final TaskScheduler taskScheduler;
+	private final EventBus eventBus;
+	private final ConnectivityChecker connectivityChecker;
+	private final MailboxApiCaller mailboxApiCaller;
+	private final MailboxApi mailboxApi;
+	private final MailboxFileManager mailboxFileManager;
+	private final MailboxProperties mailboxProperties;
+	private final MailboxFolderId folderId;
+	private final ContactId contactId;
+
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	private State state = State.CREATED;
+
+	@GuardedBy("lock")
+	@Nullable
+	private Cancellable wakeupTask = null, checkTask = null, apiCall = null;
+
+	@GuardedBy("lock")
+	@Nullable
+	private File file = null;
+
+	MailboxUploadWorker(@IoExecutor Executor ioExecutor,
+			DatabaseComponent db,
+			Clock clock,
+			TaskScheduler taskScheduler,
+			EventBus eventBus,
+			ConnectivityChecker connectivityChecker,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxProperties mailboxProperties,
+			MailboxFolderId folderId,
+			ContactId contactId) {
+		this.ioExecutor = ioExecutor;
+		this.db = db;
+		this.clock = clock;
+		this.taskScheduler = taskScheduler;
+		this.eventBus = eventBus;
+		this.connectivityChecker = connectivityChecker;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxFileManager = mailboxFileManager;
+		this.mailboxProperties = mailboxProperties;
+		this.folderId = folderId;
+		this.contactId = contactId;
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		synchronized (lock) {
+			// Don't allow the worker to be reused
+			if (state != State.CREATED) return;
+			state = State.CHECKING_FOR_DATA;
+		}
+		ioExecutor.execute(this::checkForDataToSend);
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		Cancellable wakeupTask, checkTask, apiCall;
+		File file;
+		synchronized (lock) {
+			state = State.DESTROYED;
+			wakeupTask = this.wakeupTask;
+			this.wakeupTask = null;
+			checkTask = this.checkTask;
+			this.checkTask = null;
+			apiCall = this.apiCall;
+			this.apiCall = null;
+			file = this.file;
+			this.file = null;
+		}
+		if (wakeupTask != null) wakeupTask.cancel();
+		if (checkTask != null) checkTask.cancel();
+		if (apiCall != null) apiCall.cancel();
+		if (file != null) delete(file);
+		connectivityChecker.removeObserver(this);
+		eventBus.removeListener(this);
+	}
+
+	@IoExecutor
+	private void checkForDataToSend() {
+		synchronized (lock) {
+			checkTask = null;
+			if (state != State.CHECKING_FOR_DATA) return;
+		}
+		LOG.info("Checking for data to send");
+		try {
+			db.transaction(true, txn -> {
+				long nextSendTime;
+				if (db.containsAcksToSend(txn, contactId)) {
+					nextSendTime = 0L;
+				} else {
+					nextSendTime = db.getNextSendTime(txn, contactId,
+							MAX_LATENCY);
+				}
+				// Handle the result on the event executor to avoid races with
+				// incoming events
+				txn.attach(() -> handleNextSendTime(nextSendTime));
+			});
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@EventExecutor
+	private void handleNextSendTime(long nextSendTime) {
+		if (nextSendTime == Long.MAX_VALUE) {
+			// Nothing is sendable now or due to be sent in the future. Wait
+			// for an event indicating that new data may be ready to send
+			waitForDataToSend();
+		} else {
+			// Work out the delay until data's ready to send (may be negative)
+			long delay = nextSendTime - clock.currentTimeMillis();
+			if (delay > 0) {
+				// Schedule a wakeup when data will be ready to send. If an
+				// event is received in the meantime indicating that new data
+				// may be ready to send, we'll cancel the wakeup
+				scheduleWakeup(delay);
+			} else {
+				// Data is ready to send now
+				checkConnectivity();
+			}
+		}
+	}
+
+	@EventExecutor
+	private void waitForDataToSend() {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.WAITING_FOR_DATA;
+			LOG.info("Waiting for data to send");
+		}
+	}
+
+	@EventExecutor
+	private void scheduleWakeup(long delay) {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.WAITING_FOR_DATA;
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Scheduling wakeup in " + delay + " ms");
+			}
+			wakeupTask = taskScheduler.schedule(this::wakeUp, ioExecutor,
+					delay, MILLISECONDS);
+		}
+	}
+
+	@IoExecutor
+	private void wakeUp() {
+		LOG.info("Woke up");
+		synchronized (lock) {
+			wakeupTask = null;
+			if (state != State.WAITING_FOR_DATA) return;
+			state = State.CHECKING_FOR_DATA;
+		}
+		checkForDataToSend();
+	}
+
+	@EventExecutor
+	private void checkConnectivity() {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.CONNECTIVITY_CHECK;
+		}
+		LOG.info("Checking connectivity");
+		// Avoid leaking observer in case destroy() is called concurrently
+		// before observer is added
+		connectivityChecker.checkConnectivity(mailboxProperties, this);
+		boolean destroyed;
+		synchronized (lock) {
+			destroyed = state == State.DESTROYED;
+		}
+		if (destroyed) connectivityChecker.removeObserver(this);
+	}
+
+	@Override
+	public void onConnectivityCheckSucceeded() {
+		LOG.info("Connectivity check succeeded");
+		synchronized (lock) {
+			if (state != State.CONNECTIVITY_CHECK) return;
+			state = State.WRITING_UPLOADING;
+		}
+		ioExecutor.execute(this::writeAndUploadFile);
+	}
+
+	@IoExecutor
+	private void writeAndUploadFile() {
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+		}
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+		File file;
+		try {
+			file = mailboxFileManager.createAndWriteTempFileForUpload(
+					contactId, sessionRecord);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			// Try again after a delay
+			synchronized (lock) {
+				if (state != State.WRITING_UPLOADING) return;
+				state = State.CHECKING_FOR_DATA;
+				checkTask = taskScheduler.schedule(this::checkForDataToSend,
+						ioExecutor, RETRY_DELAY_MS, MILLISECONDS);
+			}
+			return;
+		}
+		boolean deleteFile = false;
+		synchronized (lock) {
+			if (state == State.WRITING_UPLOADING) {
+				this.file = file;
+				apiCall = mailboxApiCaller.retryWithBackoff(
+						new SimpleApiCall(() -> apiCallUploadFile(file,
+								sessionRecord)));
+			} else {
+				deleteFile = true;
+			}
+		}
+		if (deleteFile) delete(file);
+	}
+
+	@IoExecutor
+	private void apiCallUploadFile(File file,
+			OutgoingSessionRecord sessionRecord)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+		}
+		LOG.info("Uploading file");
+		mailboxApi.addFile(mailboxProperties, folderId, file);
+		markMessagesSentOrAcked(sessionRecord);
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+			state = State.CHECKING_FOR_DATA;
+			apiCall = null;
+			this.file = null;
+		}
+		delete(file);
+		checkForDataToSend();
+	}
+
+	private void markMessagesSentOrAcked(OutgoingSessionRecord sessionRecord) {
+		Collection<MessageId> acked = sessionRecord.getAckedIds();
+		Collection<MessageId> sent = sessionRecord.getSentIds();
+		try {
+			db.transaction(false, txn -> {
+				if (!acked.isEmpty()) {
+					db.setAckSent(txn, contactId, acked);
+				}
+				if (!sent.isEmpty()) {
+					db.setMessagesSent(txn, contactId, sent, MAX_LATENCY);
+				}
+			});
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof MessageToAckEvent) {
+			MessageToAckEvent m = (MessageToAckEvent) e;
+			if (m.getContactId().equals(contactId)) {
+				LOG.info("Message to ack");
+				onDataToSend();
+			}
+		} else if (e instanceof MessageSharedEvent) {
+			LOG.info("Message shared");
+			onDataToSend();
+		} else if (e instanceof GroupVisibilityUpdatedEvent) {
+			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
+			if (g.getVisibility() == SHARED &&
+					g.getAffectedContacts().contains(contactId)) {
+				LOG.info("Group shared");
+				onDataToSend();
+			}
+		}
+	}
+
+	@EventExecutor
+	private void onDataToSend() {
+		Cancellable wakeupTask;
+		synchronized (lock) {
+			if (state != State.WAITING_FOR_DATA) return;
+			state = State.CHECKING_FOR_DATA;
+			wakeupTask = this.wakeupTask;
+			this.wakeupTask = null;
+			// Delay the check to avoid creating lots of small files
+			checkTask = taskScheduler.schedule(this::checkForDataToSend,
+					ioExecutor, CHECK_DELAY_MS, MILLISECONDS);
+		}
+		// If we had scheduled a wakeup when data was due to be sent, cancel it
+		if (wakeupTask != null) wakeupTask.cancel();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxWorker.java

@@ -0,0 +1,23 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * A worker that downloads files from a contact's mailbox.
+ */
+@ThreadSafe
+@NotNullByDefault
+interface MailboxWorker {
+
+	/**
+	 * Asynchronously starts the worker.
+	 */
+	void start();
+
+	/**
+	 * Destroys the worker and cancels any pending tasks or retries.
+	 */
+	void destroy();
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxWorkerFactory.java

@@ -0,0 +1,31 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+@ThreadSafe
+@NotNullByDefault
+interface MailboxWorkerFactory {
+
+	MailboxWorker createUploadWorker(ConnectivityChecker connectivityChecker,
+			MailboxProperties properties, MailboxFolderId folderId,
+			ContactId contactId);
+
+	MailboxWorker createDownloadWorkerForContactMailbox(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor,
+			MailboxProperties properties);
+
+	MailboxWorker createDownloadWorkerForOwnMailbox(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor,
+			MailboxProperties properties);
+
+	MailboxWorker createContactListWorkerForOwnMailbox(
+			ConnectivityChecker connectivityChecker,
+			MailboxProperties properties);
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxWorkerFactoryImpl.java

@@ -0,0 +1,95 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+
+import java.util.concurrent.Executor;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+@Immutable
+@NotNullByDefault
+class MailboxWorkerFactoryImpl implements MailboxWorkerFactory {
+
+	private final Executor ioExecutor;
+	private final DatabaseComponent db;
+	private final Clock clock;
+	private final TaskScheduler taskScheduler;
+	private final EventBus eventBus;
+	private final MailboxApiCaller mailboxApiCaller;
+	private final MailboxApi mailboxApi;
+	private final MailboxFileManager mailboxFileManager;
+	private final MailboxUpdateManager mailboxUpdateManager;
+
+	@Inject
+	MailboxWorkerFactoryImpl(@IoExecutor Executor ioExecutor,
+			DatabaseComponent db,
+			Clock clock,
+			TaskScheduler taskScheduler,
+			EventBus eventBus,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxUpdateManager mailboxUpdateManager) {
+		this.ioExecutor = ioExecutor;
+		this.db = db;
+		this.clock = clock;
+		this.taskScheduler = taskScheduler;
+		this.eventBus = eventBus;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxFileManager = mailboxFileManager;
+		this.mailboxUpdateManager = mailboxUpdateManager;
+	}
+
+	@Override
+	public MailboxWorker createUploadWorker(
+			ConnectivityChecker connectivityChecker,
+			MailboxProperties properties, MailboxFolderId folderId,
+			ContactId contactId) {
+		MailboxUploadWorker worker = new MailboxUploadWorker(ioExecutor, db,
+				clock, taskScheduler, eventBus, connectivityChecker,
+				mailboxApiCaller, mailboxApi, mailboxFileManager,
+				properties, folderId, contactId);
+		eventBus.addListener(worker);
+		return worker;
+	}
+
+	@Override
+	public MailboxWorker createDownloadWorkerForContactMailbox(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor,
+			MailboxProperties properties) {
+		return new ContactMailboxDownloadWorker(connectivityChecker,
+				reachabilityMonitor, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, properties);
+	}
+
+	@Override
+	public MailboxWorker createDownloadWorkerForOwnMailbox(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor,
+			MailboxProperties properties) {
+		return new OwnMailboxDownloadWorker(connectivityChecker,
+				reachabilityMonitor, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, properties);
+	}
+
+	@Override
+	public MailboxWorker createContactListWorkerForOwnMailbox(
+			ConnectivityChecker connectivityChecker,
+			MailboxProperties properties) {
+		return new OwnMailboxContactListWorker(ioExecutor, db, eventBus,
+				connectivityChecker, mailboxApiCaller, mailboxApi,
+				mailboxUpdateManager, properties);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxClient.java

@@ -0,0 +1,154 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Logger.getLogger;
+
+@ThreadSafe
+@NotNullByDefault
+class OwnMailboxClient implements MailboxClient {
+
+	private static final Logger LOG =
+			getLogger(OwnMailboxClient.class.getName());
+
+	private final MailboxWorkerFactory workerFactory;
+	private final ConnectivityChecker connectivityChecker;
+	private final TorReachabilityMonitor reachabilityMonitor;
+	private final MailboxWorker contactListWorker;
+	private final Object lock = new Object();
+
+	/**
+	 * Upload workers: one worker per contact assigned for upload.
+	 */
+	@GuardedBy("lock")
+	private final Map<ContactId, MailboxWorker> uploadWorkers = new HashMap<>();
+
+	/**
+	 * Download worker: shared between all contacts assigned for download.
+	 * Null if no contacts are assigned for download.
+	 */
+	@GuardedBy("lock")
+	@Nullable
+	private MailboxWorker downloadWorker = null;
+
+	/**
+	 * IDs of contacts assigned for download, so that we know when to
+	 * create/destroy the download worker.
+	 */
+	@GuardedBy("lock")
+	private final Set<ContactId> assignedForDownload = new HashSet<>();
+
+	OwnMailboxClient(MailboxWorkerFactory workerFactory,
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor reachabilityMonitor,
+			MailboxProperties properties) {
+		if (!properties.isOwner()) throw new IllegalArgumentException();
+		this.workerFactory = workerFactory;
+		this.connectivityChecker = connectivityChecker;
+		this.reachabilityMonitor = reachabilityMonitor;
+		contactListWorker = workerFactory.createContactListWorkerForOwnMailbox(
+				connectivityChecker, properties);
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		contactListWorker.start();
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		List<MailboxWorker> uploadWorkers;
+		MailboxWorker downloadWorker;
+		synchronized (lock) {
+			uploadWorkers = new ArrayList<>(this.uploadWorkers.values());
+			this.uploadWorkers.clear();
+			downloadWorker = this.downloadWorker;
+			this.downloadWorker = null;
+		}
+		// Destroy the workers (with apologies to Mr Marx and Mr Engels)
+		for (MailboxWorker worker : uploadWorkers) worker.destroy();
+		if (downloadWorker != null) downloadWorker.destroy();
+		contactListWorker.destroy();
+	}
+
+	@Override
+	public void assignContactForUpload(ContactId contactId,
+			MailboxProperties properties, MailboxFolderId folderId) {
+		LOG.info("Contact assigned for upload");
+		if (!properties.isOwner()) throw new IllegalArgumentException();
+		MailboxWorker uploadWorker = workerFactory.createUploadWorker(
+				connectivityChecker, properties, folderId, contactId);
+		synchronized (lock) {
+			MailboxWorker old = uploadWorkers.put(contactId, uploadWorker);
+			if (old != null) throw new IllegalStateException();
+		}
+		uploadWorker.start();
+	}
+
+	@Override
+	public void deassignContactForUpload(ContactId contactId) {
+		LOG.info("Contact deassigned for upload");
+		MailboxWorker uploadWorker;
+		synchronized (lock) {
+			uploadWorker = uploadWorkers.remove(contactId);
+		}
+		if (uploadWorker != null) uploadWorker.destroy();
+	}
+
+	@Override
+	public void assignContactForDownload(ContactId contactId,
+			MailboxProperties properties, MailboxFolderId folderId) {
+		LOG.info("Contact assigned for download");
+		if (!properties.isOwner()) throw new IllegalArgumentException();
+		// Create a download worker if we don't already have one. The worker
+		// will use the API to discover which folders have files to download,
+		// so it doesn't need to track the set of assigned contacts
+		MailboxWorker toStart = null;
+		synchronized (lock) {
+			if (!assignedForDownload.add(contactId)) {
+				throw new IllegalStateException();
+			}
+			if (downloadWorker == null) {
+				toStart = workerFactory.createDownloadWorkerForOwnMailbox(
+						connectivityChecker, reachabilityMonitor, properties);
+				downloadWorker = toStart;
+			}
+		}
+		if (toStart != null) toStart.start();
+	}
+
+	@Override
+	public void deassignContactForDownload(ContactId contactId) {
+		LOG.info("Contact deassigned for download");
+		// If there are no more contacts assigned for download, destroy the
+		// download worker
+		MailboxWorker toDestroy = null;
+		synchronized (lock) {
+			if (!assignedForDownload.remove(contactId)) {
+				throw new IllegalStateException();
+			}
+			if (assignedForDownload.isEmpty()) {
+				toDestroy = downloadWorker;
+				downloadWorker = null;
+			}
+		}
+		if (toDestroy != null) toDestroy.destroy();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxConnectivityChecker.java

@@ -4,11 +4,13 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
@@ -55,11 +57,12 @@ class OwnMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 	private boolean checkConnectivityAndStoreResult(
 			MailboxProperties properties) throws DbException {
 		try {
-			if (!mailboxApi.checkStatus(properties)) throw new ApiException();
+			List<MailboxVersion> serverSupports =
+					mailboxApi.getServerSupports(properties);
 			LOG.info("Own mailbox is reachable");
 			long now = clock.currentTimeMillis();
 			db.transaction(false, txn -> mailboxSettingsManager
-					.recordSuccessfulConnection(txn, now));
+					.recordSuccessfulConnection(txn, now, serverSupports));
 			// Call the observers and cache the result
 			onConnectivityCheckSucceeded(now);
 			return false; // Don't retry

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxContactListWorker.java

@@ -0,0 +1,369 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
+import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.NoSuchContactException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventExecutor;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
+import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxContact;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Set;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@ThreadSafe
+@NotNullByDefault
+class OwnMailboxContactListWorker
+		implements MailboxWorker, ConnectivityObserver, EventListener {
+
+	/**
+	 * When the worker is started it waits for a connectivity check, then
+	 * fetches the remote contact list and compares it to the local contact
+	 * list.
+	 * <p>
+	 * Any contacts that are missing from the remote list are added to the
+	 * mailbox's contact list, while any contacts that are missing from the
+	 * local list are removed from the mailbox's contact list.
+	 * <p>
+	 * Once the remote contact list has been brought up to date, the worker
+	 * waits for events indicating that contacts have been added or removed.
+	 * Each time an event is received, the worker updates the mailbox's
+	 * contact list and then goes back to waiting.
+	 */
+	private enum State {
+		CREATED,
+		CONNECTIVITY_CHECK,
+		FETCHING_CONTACT_LIST,
+		UPDATING_CONTACT_LIST,
+		WAITING_FOR_CHANGES,
+		DESTROYED
+	}
+
+	private static final Logger LOG =
+			getLogger(OwnMailboxContactListWorker.class.getName());
+
+	private final Executor ioExecutor;
+	private final DatabaseComponent db;
+	private final EventBus eventBus;
+	private final ConnectivityChecker connectivityChecker;
+	private final MailboxApiCaller mailboxApiCaller;
+	private final MailboxApi mailboxApi;
+	private final MailboxUpdateManager mailboxUpdateManager;
+	private final MailboxProperties mailboxProperties;
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	private State state = State.CREATED;
+
+	@GuardedBy("lock")
+	@Nullable
+	private Cancellable apiCall = null;
+
+	/**
+	 * A queue of updates waiting to be applied to the remote contact list.
+	 */
+	@GuardedBy("lock")
+	private final Queue<Update> updates = new LinkedList<>();
+
+	OwnMailboxContactListWorker(@IoExecutor Executor ioExecutor,
+			DatabaseComponent db,
+			EventBus eventBus,
+			ConnectivityChecker connectivityChecker,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxUpdateManager mailboxUpdateManager,
+			MailboxProperties mailboxProperties) {
+		if (!mailboxProperties.isOwner()) throw new IllegalArgumentException();
+		this.ioExecutor = ioExecutor;
+		this.db = db;
+		this.connectivityChecker = connectivityChecker;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxUpdateManager = mailboxUpdateManager;
+		this.mailboxProperties = mailboxProperties;
+		this.eventBus = eventBus;
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		synchronized (lock) {
+			if (state != State.CREATED) return;
+			state = State.CONNECTIVITY_CHECK;
+		}
+		// Avoid leaking observer in case destroy() is called concurrently
+		// before observer is added
+		connectivityChecker.checkConnectivity(mailboxProperties, this);
+		boolean destroyed;
+		synchronized (lock) {
+			destroyed = state == State.DESTROYED;
+		}
+		if (destroyed) connectivityChecker.removeObserver(this);
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		Cancellable apiCall;
+		synchronized (lock) {
+			state = State.DESTROYED;
+			apiCall = this.apiCall;
+			this.apiCall = null;
+		}
+		if (apiCall != null) apiCall.cancel();
+		connectivityChecker.removeObserver(this);
+		eventBus.removeListener(this);
+	}
+
+	@Override
+	public void onConnectivityCheckSucceeded() {
+		LOG.info("Connectivity check succeeded");
+		synchronized (lock) {
+			if (state != State.CONNECTIVITY_CHECK) return;
+			state = State.FETCHING_CONTACT_LIST;
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(this::apiCallFetchContactList));
+		}
+	}
+
+	@IoExecutor
+	private void apiCallFetchContactList() throws IOException, ApiException {
+		synchronized (lock) {
+			if (state != State.FETCHING_CONTACT_LIST) return;
+		}
+		LOG.info("Fetching remote contact list");
+		Collection<ContactId> remote =
+				mailboxApi.getContacts(mailboxProperties);
+		ioExecutor.execute(() -> loadLocalContactList(remote));
+	}
+
+	@IoExecutor
+	private void loadLocalContactList(Collection<ContactId> remote) {
+		synchronized (lock) {
+			if (state != State.FETCHING_CONTACT_LIST) return;
+			apiCall = null;
+		}
+		LOG.info("Loading local contact list");
+		try {
+			db.transaction(true, txn -> {
+				Collection<Contact> local = db.getContacts(txn);
+				// Handle the result on the event executor to avoid races with
+				// incoming events
+				txn.attach(() -> reconcileContactLists(local, remote));
+			});
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@EventExecutor
+	private void reconcileContactLists(Collection<Contact> local,
+			Collection<ContactId> remote) {
+		Set<ContactId> localIds = new HashSet<>();
+		for (Contact c : local) localIds.add(c.getId());
+		remote = new HashSet<>(remote);
+		synchronized (lock) {
+			if (state != State.FETCHING_CONTACT_LIST) return;
+			for (ContactId c : localIds) {
+				if (!remote.contains(c)) updates.add(new Update(true, c));
+			}
+			for (ContactId c : remote) {
+				if (!localIds.contains(c)) updates.add(new Update(false, c));
+			}
+			if (updates.isEmpty()) {
+				LOG.info("Contact list is up to date");
+				state = State.WAITING_FOR_CHANGES;
+			} else {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info(updates.size() + " updates to apply");
+				}
+				state = State.UPDATING_CONTACT_LIST;
+				ioExecutor.execute(this::updateContactList);
+			}
+		}
+	}
+
+	@IoExecutor
+	private void updateContactList() {
+		Update update;
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+			update = updates.poll();
+			if (update == null) {
+				LOG.info("No more updates to process");
+				state = State.WAITING_FOR_CHANGES;
+				apiCall = null;
+				return;
+			}
+		}
+		if (update.add) loadMailboxProperties(update.contactId);
+		else removeContact(update.contactId);
+	}
+
+	@IoExecutor
+	private void loadMailboxProperties(ContactId c) {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+		}
+		LOG.info("Loading mailbox properties for contact");
+		try {
+			MailboxUpdate mailboxUpdate = db.transactionWithResult(true, txn ->
+					mailboxUpdateManager.getLocalUpdate(txn, c));
+			if (mailboxUpdate instanceof MailboxUpdateWithMailbox) {
+				addContact(c, (MailboxUpdateWithMailbox) mailboxUpdate);
+			} else {
+				// Our own mailbox was concurrently unpaired. This worker will
+				// be destroyed soon, so we can stop here
+				LOG.info("Own mailbox was unpaired");
+			}
+		} catch (NoSuchContactException e) {
+			// Contact was removed concurrently. Move on to the next update.
+			// Later we may process a removal update for this contact, which
+			// was never added to the mailbox's contact list. The removal API
+			// call should fail safely with a TolerableFailureException
+			LOG.info("No such contact");
+			updateContactList();
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@IoExecutor
+	private void addContact(ContactId c, MailboxUpdateWithMailbox withMailbox) {
+		MailboxProperties props = withMailbox.getMailboxProperties();
+		MailboxContact contact = new MailboxContact(c, props.getAuthToken(),
+				requireNonNull(props.getInboxId()),
+				requireNonNull(props.getOutboxId()));
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
+					apiCallAddContact(contact)));
+		}
+	}
+
+	@IoExecutor
+	private void apiCallAddContact(MailboxContact contact)
+			throws IOException, ApiException, TolerableFailureException {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+		}
+		LOG.info("Adding contact to remote contact list");
+		mailboxApi.addContact(mailboxProperties, contact);
+		updateContactList();
+	}
+
+	@IoExecutor
+	private void removeContact(ContactId c) {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
+					apiCallRemoveContact(c)));
+		}
+	}
+
+	@IoExecutor
+	private void apiCallRemoveContact(ContactId c)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST) return;
+		}
+		LOG.info("Removing contact from remote contact list");
+		try {
+			mailboxApi.deleteContact(mailboxProperties, c);
+		} catch (TolerableFailureException e) {
+			// Catch this so we can continue to the next update
+			LOG.warning("Contact does not exist");
+		}
+		updateContactList();
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof ContactAddedEvent) {
+			LOG.info("Contact added");
+			onContactAdded(((ContactAddedEvent) e).getContactId());
+		} else if (e instanceof ContactRemovedEvent) {
+			LOG.info("Contact removed");
+			onContactRemoved(((ContactRemovedEvent) e).getContactId());
+		}
+	}
+
+	@EventExecutor
+	private void onContactAdded(ContactId c) {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST &&
+					state != State.WAITING_FOR_CHANGES) {
+				return;
+			}
+			updates.add(new Update(true, c));
+			if (state == State.WAITING_FOR_CHANGES) {
+				state = State.UPDATING_CONTACT_LIST;
+				ioExecutor.execute(this::updateContactList);
+			}
+		}
+	}
+
+	@EventExecutor
+	private void onContactRemoved(ContactId c) {
+		synchronized (lock) {
+			if (state != State.UPDATING_CONTACT_LIST &&
+					state != State.WAITING_FOR_CHANGES) {
+				return;
+			}
+			updates.add(new Update(false, c));
+			if (state == State.WAITING_FOR_CHANGES) {
+				state = State.UPDATING_CONTACT_LIST;
+				ioExecutor.execute(this::updateContactList);
+			}
+		}
+	}
+
+	/**
+	 * An update that should be applied to the remote contact list.
+	 */
+	private static class Update {
+
+		/**
+		 * True if the contact should be added, false if the contact should be
+		 * removed.
+		 */
+		private final boolean add;
+		private final ContactId contactId;
+
+		private Update(boolean add, ContactId contactId) {
+			this.add = add;
+			this.contactId = contactId;
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxDownloadWorker.java

@@ -0,0 +1,148 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.Collections.shuffle;
+import static java.util.logging.Level.INFO;
+
+@ThreadSafe
+@NotNullByDefault
+class OwnMailboxDownloadWorker extends MailboxDownloadWorker {
+
+	/**
+	 * The maximum number of files that will be downloaded before checking
+	 * again for folders with available files. This ensures that if a file
+	 * arrives during a download cycle, its folder will be checked within a
+	 * reasonable amount of time even if some other folder has a very large
+	 * number of files.
+	 * <p>
+	 * Package access for testing.
+	 */
+	static final int MAX_ROUND_ROBIN_FILES = 1000;
+
+	OwnMailboxDownloadWorker(
+			ConnectivityChecker connectivityChecker,
+			TorReachabilityMonitor torReachabilityMonitor,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxProperties mailboxProperties) {
+		super(connectivityChecker, torReachabilityMonitor, mailboxApiCaller,
+				mailboxApi, mailboxFileManager, mailboxProperties);
+		if (!mailboxProperties.isOwner()) throw new IllegalArgumentException();
+	}
+
+	@Override
+	protected ApiCall createApiCallForDownloadCycle() {
+		return new SimpleApiCall(this::apiCallListFolders);
+	}
+
+	private void apiCallListFolders() throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		LOG.info("Listing folders with available files");
+		List<MailboxFolderId> folders =
+				mailboxApi.getFolders(mailboxProperties);
+		if (folders.isEmpty()) onDownloadCycleFinished();
+		else listNextFolder(new LinkedList<>(folders), new HashMap<>());
+	}
+
+	/**
+	 * Removes the next folder from `queue` and starts a task to list the
+	 * files in the folder and add them to `available`.
+	 */
+	private void listNextFolder(Queue<MailboxFolderId> queue,
+			Map<MailboxFolderId, Queue<MailboxFile>> available) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+			MailboxFolderId folder = queue.remove();
+			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
+					apiCallListFolder(folder, queue, available)));
+		}
+	}
+
+	private void apiCallListFolder(MailboxFolderId folder,
+			Queue<MailboxFolderId> queue,
+			Map<MailboxFolderId, Queue<MailboxFile>> available)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		LOG.info("Listing folder");
+		try {
+			List<MailboxFile> files =
+					mailboxApi.getFiles(mailboxProperties, folder);
+			if (!files.isEmpty()) {
+				available.put(folder, new LinkedList<>(files));
+			}
+		} catch (TolerableFailureException e) {
+			LOG.warning("Folder does not exist");
+		}
+		if (queue.isEmpty()) {
+			LOG.info("Finished listing folders");
+			if (available.isEmpty()) onDownloadCycleFinished();
+			else createDownloadQueue(available);
+		} else {
+			listNextFolder(queue, available);
+		}
+	}
+
+	/**
+	 * Visits the given folders in round-robin order to create a queue of up to
+	 * {@link #MAX_ROUND_ROBIN_FILES} to download.
+	 */
+	private void createDownloadQueue(
+			Map<MailboxFolderId, Queue<MailboxFile>> available) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		if (LOG.isLoggable(INFO)) {
+			LOG.info(available.size() + " folders have available files");
+		}
+		Queue<FolderFile> queue = createRoundRobinQueue(available);
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Downloading " + queue.size() + " files");
+		}
+		downloadNextFile(queue);
+	}
+
+	// Package access for testing
+	Queue<FolderFile> createRoundRobinQueue(
+			Map<MailboxFolderId, Queue<MailboxFile>> available) {
+		List<MailboxFolderId> roundRobin = new ArrayList<>(available.keySet());
+		// Shuffle the folders so we don't always favour the same folders
+		shuffle(roundRobin);
+		Queue<FolderFile> queue = new LinkedList<>();
+		while (queue.size() < MAX_ROUND_ROBIN_FILES && !available.isEmpty()) {
+			Iterator<MailboxFolderId> it = roundRobin.iterator();
+			while (queue.size() < MAX_ROUND_ROBIN_FILES && it.hasNext()) {
+				MailboxFolderId folder = it.next();
+				Queue<MailboxFile> files = available.get(folder);
+				MailboxFile file = files.remove();
+				queue.add(new FolderFile(folder, file.name));
+				if (files.isEmpty()) {
+					available.remove(folder);
+					it.remove();
+				}
+			}
+		}
+		return queue;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/SimpleApiCall.java

@@ -16,17 +16,20 @@ import static org.briarproject.bramble.util.LogUtils.logException;
  * Convenience class for making simple API calls that don't return values.
  */
 @NotNullByDefault
-public abstract class SimpleApiCall implements ApiCall {
+class SimpleApiCall implements ApiCall {
 
 	private static final Logger LOG = getLogger(SimpleApiCall.class.getName());
 
-	abstract void tryToCallApi()
-			throws IOException, ApiException, TolerableFailureException;
+	private final Attempt attempt;
+
+	SimpleApiCall(Attempt attempt) {
+		this.attempt = attempt;
+	}
 
 	@Override
 	public boolean callApi() {
 		try {
-			tryToCallApi();
+			attempt.tryToCallApi();
 			return false; // Succeeded, don't retry
 		} catch (IOException | ApiException e) {
 			logException(LOG, WARNING, e);
@@ -36,4 +39,17 @@ public abstract class SimpleApiCall implements ApiCall {
 			return false; // Failed tolerably, don't retry
 		}
 	}
+
+	interface Attempt {
+
+		/**
+		 * Makes a single attempt to call an API endpoint. If this method
+		 * throws an {@link IOException} or an {@link ApiException}, the call
+		 * will be retried. If it throws a {@link TolerableFailureException}
+		 * or returns without throwing an exception, the call will not be
+		 * retried.
+		 */
+		void tryToCallApi()
+				throws IOException, ApiException, TolerableFailureException;
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/TorReachabilityMonitor.java

@@ -38,6 +38,12 @@ interface TorReachabilityMonitor {
 	 */
 	void addOneShotObserver(TorReachabilityObserver o);
 
+	/**
+	 * Removes an observer that was added via
+	 * {@link #addOneShotObserver(TorReachabilityObserver)}.
+	 */
+	void removeObserver(TorReachabilityObserver o);
+
 	interface TorReachabilityObserver {
 
 		void onTorReachable();

bramble-core/src/main/java/org/briarproject/bramble/mailbox/TorReachabilityMonitorImpl.java

@@ -87,6 +87,14 @@ class TorReachabilityMonitorImpl
 		if (callNow) o.onTorReachable();
 	}
 
+	@Override
+	public void removeObserver(TorReachabilityObserver o) {
+		synchronized (lock) {
+			if (destroyed) return;
+			observers.remove(o);
+		}
+	}
+
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof TransportActiveEvent) {

bramble-core/src/main/java/org/briarproject/bramble/mailbox/UrlConverter.java

@@ -0,0 +1,17 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * An interface for converting an onion address to an HTTP URL, allowing the
+ * conversion to be customised for integration tests.
+ */
+@NotNullByDefault
+interface UrlConverter {
+
+   /**
+    * Converts a raw onion address, excluding the .onion suffix, into an
+    * HTTP URL.
+    */
+   String convertOnionToBaseUrl(String onion);
+}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/UrlConverterImpl.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.inject.Inject;
+
+@NotNullByDefault
+class UrlConverterImpl implements UrlConverter {
+
+	@Inject
+	UrlConverterImpl() {
+	}
+
+	@Override
+	public String convertOnionToBaseUrl(String onion) {
+		return "http://" + onion + ".onion";
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/AbstractBluetoothPlugin.java

@@ -427,7 +427,13 @@ abstract class AbstractBluetoothPlugin<S, SS> implements BluetoothPlugin,
 		BdfList descriptor = new BdfList();
 		descriptor.add(TRANSPORT_ID_BLUETOOTH);
 		String address = getBluetoothAddress();
-		if (address != null) descriptor.add(macToBytes(address));
+		if (address != null) {
+			try {
+				descriptor.add(macToBytes(address));
+			} catch (FormatException e) {
+				throw new RuntimeException();
+			}
+		}
 		return new BluetoothKeyAgreementListener(descriptor, ss);
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/MailboxPluginFactory.java

@@ -9,14 +9,12 @@ import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import static java.util.concurrent.TimeUnit.DAYS;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
 
 @NotNullByDefault
 public class MailboxPluginFactory implements SimplexPluginFactory {
 
-	private static final long MAX_LATENCY = DAYS.toMillis(14);
-
 	@Inject
 	MailboxPluginFactory() {
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/RemovableDriveManagerImpl.java

@@ -106,7 +106,8 @@ class RemovableDriveManagerImpl
 	@Override
 	public boolean isWriterTaskNeeded(ContactId c) throws DbException {
 		return db.transactionWithResult(true, txn ->
-				db.containsAnythingToSend(txn, c, MAX_LATENCY, true));
+				db.containsAcksToSend(txn, c) ||
+						db.containsMessagesToSend(txn, c, MAX_LATENCY, true));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPlugin.java

@@ -285,7 +285,7 @@ class LanTcpPlugin extends TcpPlugin {
 				if (ip.length == 16) addrs.add(InetAddress.getByAddress(ip));
 			}
 			return addrs;
-		} catch (IllegalArgumentException | UnknownHostException e) {
+		} catch (FormatException | UnknownHostException e) {
 			return emptyList();
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/CircumventionProvider.java

@@ -27,7 +27,7 @@ public interface CircumventionProvider {
 	 * Countries where bridge connections are likely to work.
 	 * Should be a subset of {@link #BLOCKED} and the union of
 	 * {@link #DEFAULT_BRIDGES}, {@link #NON_DEFAULT_BRIDGES} and
-	 * {@link #MEEK_BRIDGES}.
+	 * {@link #DPI_BRIDGES}.
 	 */
 	String[] BRIDGES = {"BY", "CN", "EG", "IR", "RU", "TM", "VE"};
 
@@ -44,10 +44,10 @@ public interface CircumventionProvider {
 	String[] NON_DEFAULT_BRIDGES = {"BY", "RU", "TM"};
 
 	/**
-	 * Countries where obfs4 and vanilla bridges won't work and meek is needed.
-	 * Should be a subset of {@link #BRIDGES}.
+	 * Countries where vanilla bridges are blocked via DPI but non-default
+	 * obfs4 bridges and meek may work. Should be a subset of {@link #BRIDGES}.
 	 */
-	String[] MEEK_BRIDGES = {"CN", "IR"};
+	String[] DPI_BRIDGES = {"CN", "IR"};
 
 	/**
 	 * Returns true if vanilla Tor connections are blocked in the given country.

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/CircumventionProviderImpl.java

@@ -14,7 +14,6 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.Arrays.asList;
-import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.MEEK;
@@ -35,8 +34,8 @@ class CircumventionProviderImpl implements CircumventionProvider {
 			new HashSet<>(asList(DEFAULT_BRIDGES));
 	private static final Set<String> NON_DEFAULT_BRIDGE_COUNTRIES =
 			new HashSet<>(asList(NON_DEFAULT_BRIDGES));
-	private static final Set<String> MEEK_COUNTRIES =
-			new HashSet<>(asList(MEEK_BRIDGES));
+	private static final Set<String> DPI_COUNTRIES =
+			new HashSet<>(asList(DPI_BRIDGES));
 
 	@Inject
 	CircumventionProviderImpl() {
@@ -58,8 +57,8 @@ class CircumventionProviderImpl implements CircumventionProvider {
 			return asList(DEFAULT_OBFS4, VANILLA);
 		} else if (NON_DEFAULT_BRIDGE_COUNTRIES.contains(countryCode)) {
 			return asList(NON_DEFAULT_OBFS4, VANILLA);
-		} else if (MEEK_COUNTRIES.contains(countryCode)) {
-			return singletonList(MEEK);
+		} else if (DPI_COUNTRIES.contains(countryCode)) {
+			return asList(NON_DEFAULT_OBFS4, MEEK);
 		} else {
 			return asList(DEFAULT_OBFS4, VANILLA);
 		}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -65,6 +65,7 @@ import javax.annotation.concurrent.ThreadSafe;
 import javax.net.SocketFactory;
 
 import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.logging.Level.INFO;
@@ -93,9 +94,7 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V3;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_BATTERY;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_COUNTRY_BLOCKED;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_MOBILE_DATA;
-import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.MEEK;
-import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.NON_DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.TorRendezvousCrypto.SEED_BYTES;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
@@ -107,7 +106,7 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 @ParametersNotNullByDefault
 abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
-	private static final Logger LOG = getLogger(TorPlugin.class.getName());
+	protected static final Logger LOG = getLogger(TorPlugin.class.getName());
 
 	private static final String[] EVENTS = {
 			"CIRC",
@@ -124,7 +123,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private static final int COOKIE_POLLING_INTERVAL_MS = 200;
 	private static final Pattern ONION_V3 = Pattern.compile("[a-z2-7]{56}");
 
-	private final Executor ioExecutor, wakefulIoExecutor;
+	protected final Executor ioExecutor;
+	private final Executor wakefulIoExecutor;
 	private final Executor connectionStatusExecutor;
 	private final NetworkManager networkManager;
 	private final LocationUtils locationUtils;
@@ -238,8 +238,14 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 		// Load the settings
 		settings = callback.getSettings();
-		// Install or update the assets if necessary
-		if (!assetsAreUpToDate()) installAssets();
+		try {
+			// Install or update the assets if necessary
+			if (!assetsAreUpToDate()) installAssets();
+			// Start from the default config every time
+			extract(getConfigInputStream(), configFile);
+		} catch (IOException e) {
+			throw new PluginException(e);
+		}
 		if (cookieFile.exists() && !cookieFile.delete())
 			LOG.warning("Old auth cookie not deleted");
 		// Start a new Tor process
@@ -254,34 +260,15 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		Map<String, String> env = pb.environment();
 		env.put("HOME", torDirectory.getAbsolutePath());
 		pb.directory(torDirectory);
+		pb.redirectErrorStream(true);
 		try {
 			torProcess = pb.start();
 		} catch (SecurityException | IOException e) {
 			throw new PluginException(e);
 		}
-		// Log the process's standard output until it detaches
-		if (LOG.isLoggable(INFO)) {
-			Scanner stdout = new Scanner(torProcess.getInputStream());
-			Scanner stderr = new Scanner(torProcess.getErrorStream());
-			while (stdout.hasNextLine() || stderr.hasNextLine()) {
-				if (stdout.hasNextLine()) {
-					LOG.info(stdout.nextLine());
-				}
-				if (stderr.hasNextLine()) {
-					LOG.info(stderr.nextLine());
-				}
-			}
-			stdout.close();
-			stderr.close();
-		}
 		try {
-			// Wait for the process to detach or exit
-			int exit = torProcess.waitFor();
-			if (exit != 0) {
-				if (LOG.isLoggable(WARNING))
-					LOG.warning("Tor exited with value " + exit);
-				throw new PluginException();
-			}
+			// Wait for the Tor process to start
+			waitForTorToStart(torProcess);
 			// Wait for the auth cookie file to be created/updated
 			long start = clock.currentTimeMillis();
 			while (cookieFile.length() < 32) {
@@ -320,7 +307,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			info = controlConnection.getInfo("status/circuit-established");
 			if ("1".equals(info)) {
 				LOG.info("Tor has already built a circuit");
-				state.getAndSetCircuitBuilt(true);
+				state.setCircuitBuilt(true);
 			}
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
@@ -339,25 +326,20 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		return doneFile.lastModified() > getLastUpdateTime();
 	}
 
-	private void installAssets() throws PluginException {
-		try {
-			// The done file may already exist from a previous installation
-			//noinspection ResultOfMethodCallIgnored
-			doneFile.delete();
-			// The GeoIP file may exist from a previous installation - we can
-			// save some space by deleting it.
-			// TODO: Remove after a reasonable migration period
-			//  (added 2022-03-29)
-			//noinspection ResultOfMethodCallIgnored
-			geoIpFile.delete();
-			installTorExecutable();
-			installObfs4Executable();
-			extract(getConfigInputStream(), configFile);
-			if (!doneFile.createNewFile())
-				LOG.warning("Failed to create done file");
-		} catch (IOException e) {
-			throw new PluginException(e);
-		}
+	private void installAssets() throws IOException {
+		// The done file may already exist from a previous installation
+		//noinspection ResultOfMethodCallIgnored
+		doneFile.delete();
+		// The GeoIP file may exist from a previous installation - we can
+		// save some space by deleting it.
+		// TODO: Remove after a reasonable migration period
+		//  (added 2022-03-29)
+		//noinspection ResultOfMethodCallIgnored
+		geoIpFile.delete();
+		installTorExecutable();
+		installObfs4Executable();
+		if (!doneFile.createNewFile())
+			LOG.warning("Failed to create done file");
 	}
 
 	protected void extract(InputStream in, File dest) throws IOException {
@@ -397,7 +379,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		return zin;
 	}
 
-	private static void append(StringBuilder strb, String name, int value) {
+	private static void append(StringBuilder strb, String name, Object value) {
 		strb.append(name);
 		strb.append(" ");
 		strb.append(value);
@@ -405,13 +387,21 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private InputStream getConfigInputStream() {
+		File dataDirectory = new File(torDirectory, ".tor");
 		StringBuilder strb = new StringBuilder();
 		append(strb, "ControlPort", torControlPort);
 		append(strb, "CookieAuthentication", 1);
+		append(strb, "DataDirectory", dataDirectory.getAbsolutePath());
 		append(strb, "DisableNetwork", 1);
 		append(strb, "RunAsDaemon", 1);
 		append(strb, "SafeSocks", 1);
 		append(strb, "SocksPort", torSocksPort);
+		strb.append("GeoIPFile\n");
+		strb.append("GeoIPv6File\n");
+		append(strb, "ConnectionPadding", 0);
+		String obfs4Path = getObfs4ExecutableFile().getAbsolutePath();
+		append(strb, "ClientTransportPlugin obfs4 exec", obfs4Path);
+		append(strb, "ClientTransportPlugin meek_lite exec", obfs4Path);
 		//noinspection CharsetObjectCanBeUsed
 		return new ByteArrayInputStream(
 				strb.toString().getBytes(Charset.forName("UTF-8")));
@@ -442,6 +432,23 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	protected void waitForTorToStart(Process torProcess)
+			throws InterruptedException, PluginException {
+		Scanner stdout = new Scanner(torProcess.getInputStream());
+		// Log the first line of stdout (contains Tor and library versions)
+		if (stdout.hasNextLine()) LOG.info(stdout.nextLine());
+		// Read the process's stdout (and redirected stderr) until it detaches
+		while (stdout.hasNextLine()) stdout.nextLine();
+		stdout.close();
+		// Wait for the process to detach or exit
+		int exit = torProcess.waitFor();
+		if (exit != 0) {
+			if (LOG.isLoggable(WARNING))
+				LOG.warning("Tor exited with value " + exit);
+			throw new PluginException();
+		}
+	}
+
 	private void bind() {
 		ioExecutor.execute(() -> {
 			// If there's already a port number stored in config, reuse it
@@ -544,7 +551,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	protected void enableNetwork(boolean enable) throws IOException {
-		state.enableNetwork(enable);
+		if (!state.enableNetwork(enable)) return; // Unchanged
 		try {
 			controlConnection.setConf("DisableNetwork", enable ? "0" : "1");
 		} catch (TorNotRunningException e) {
@@ -552,28 +559,20 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
-	private void enableBridges(boolean enable, List<BridgeType> bridgeTypes)
+	private void enableBridges(List<BridgeType> bridgeTypes)
 			throws IOException {
+		if (!state.setBridgeTypes(bridgeTypes)) return; // Unchanged
 		try {
-			if (enable) {
+			if (bridgeTypes.isEmpty()) {
+				controlConnection.setConf("UseBridges", "0");
+				controlConnection.resetConf(singletonList("Bridge"));
+			} else {
 				Collection<String> conf = new ArrayList<>();
 				conf.add("UseBridges 1");
-				File obfs4File = getObfs4ExecutableFile();
-				if (bridgeTypes.contains(MEEK)) {
-					conf.add("ClientTransportPlugin meek_lite exec " +
-							obfs4File.getAbsolutePath());
-				}
-				if (bridgeTypes.contains(DEFAULT_OBFS4) ||
-						bridgeTypes.contains(NON_DEFAULT_OBFS4)) {
-					conf.add("ClientTransportPlugin obfs4 exec " +
-							obfs4File.getAbsolutePath());
-				}
 				for (BridgeType bridgeType : bridgeTypes) {
 					conf.addAll(circumventionProvider.getBridges(bridgeType));
 				}
 				controlConnection.setConf(conf);
-			} else {
-				controlConnection.setConf("UseBridges", "0");
 			}
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
@@ -587,7 +586,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (controlSocket != null && controlConnection != null) {
 			try {
 				LOG.info("Stopping Tor");
-				controlConnection.setConf("DisableNetwork", "1");
 				controlConnection.shutdownTor("TERM");
 				controlSocket.close();
 			} catch (TorNotRunningException e) {
@@ -755,7 +753,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	public void circuitStatus(String status, String id, String path) {
 		// In case of races between receiving CIRCUIT_ESTABLISHED and setting
 		// DisableNetwork, set our circuitBuilt flag if not already set
-		if (status.equals("BUILT") && !state.getAndSetCircuitBuilt(true)) {
+		if (status.equals("BUILT") && state.setCircuitBuilt(true)) {
 			LOG.info("Circuit built");
 			backoff.reset();
 		}
@@ -802,6 +800,13 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	@Override
+	public void controlConnectionClosed() {
+		if (state.isTorRunning()) {
+			throw new RuntimeException("Control connection closed");
+		}
+	}
+
 	private String removeSeverity(String msg) {
 		return msg.replaceFirst("[^ ]+ ", "");
 	}
@@ -812,12 +817,12 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			state.setBootstrapped();
 			backoff.reset();
 		} else if (msg.startsWith("CIRCUIT_ESTABLISHED")) {
-			if (!state.getAndSetCircuitBuilt(true)) {
+			if (state.setCircuitBuilt(true)) {
 				LOG.info("Circuit built");
 				backoff.reset();
 			}
 		} else if (msg.startsWith("CIRCUIT_NOT_ESTABLISHED")) {
-			if (state.getAndSetCircuitBuilt(false)) {
+			if (state.setCircuitBuilt(false)) {
 				LOG.info("Circuit not built");
 				// TODO: Disable and re-enable network to prompt Tor to rebuild
 				//  its guard/bridge connections? This will also close any
@@ -908,10 +913,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 
 			int reasonsDisabled = 0;
-			boolean enableNetwork = false, enableBridges = false;
-			boolean enableConnectionPadding = false;
-			List<BridgeType> bridgeTypes =
-					circumventionProvider.getSuitableBridgeTypes(country);
+			boolean enableNetwork = false, enableConnectionPadding = false;
+			List<BridgeType> bridgeTypes = emptyList();
 
 			if (!online) {
 				LOG.info("Disabling network, device is offline");
@@ -940,8 +943,12 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 					enableNetwork = true;
 					if (network == PREF_TOR_NETWORK_WITH_BRIDGES ||
 							(automatic && bridgesWork)) {
-						if (ipv6Only) bridgeTypes = singletonList(MEEK);
-						enableBridges = true;
+						if (ipv6Only) {
+							bridgeTypes = singletonList(MEEK);
+						} else {
+							bridgeTypes = circumventionProvider
+									.getSuitableBridgeTypes(country);
+						}
 						if (LOG.isLoggable(INFO)) {
 							LOG.info("Using bridge types " + bridgeTypes);
 						}
@@ -961,9 +968,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 			try {
 				if (enableNetwork) {
-					enableBridges(enableBridges, bridgeTypes);
+					enableBridges(bridgeTypes);
 					enableConnectionPadding(enableConnectionPadding);
-					useIpv6(ipv6Only);
+					enableIpv6(ipv6Only);
 				}
 				enableNetwork(enableNetwork);
 			} catch (IOException e) {
@@ -973,6 +980,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void enableConnectionPadding(boolean enable) throws IOException {
+		if (!state.enableConnectionPadding(enable)) return; // Unchanged
 		try {
 			controlConnection.setConf("ConnectionPadding", enable ? "1" : "0");
 		} catch (TorNotRunningException e) {
@@ -980,10 +988,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
-	private void useIpv6(boolean ipv6Only) throws IOException {
+	private void enableIpv6(boolean enable) throws IOException {
+		if (!state.enableIpv6(enable)) return; // Unchanged
 		try {
-			controlConnection.setConf("ClientUseIPv4", ipv6Only ? "0" : "1");
-			controlConnection.setConf("ClientUseIPv6", ipv6Only ? "1" : "0");
+			controlConnection.setConf("ClientUseIPv4", enable ? "0" : "1");
+			controlConnection.setConf("ClientUseIPv6", enable ? "1" : "0");
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
 		}
@@ -998,6 +1007,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				stopped = false,
 				networkInitialised = false,
 				networkEnabled = false,
+				paddingEnabled = false,
+				ipv6Enabled = false,
 				bootstrapped = false,
 				circuitBuilt = false,
 				settingsChecked = false;
@@ -1012,6 +1023,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@GuardedBy("this")
 		private int orConnectionsConnected = 0;
 
+		@GuardedBy("this")
+		private List<BridgeType> bridgeTypes = emptyList();
+
 		private synchronized void setStarted() {
 			started = true;
 			callback.pluginStateChanged(getState());
@@ -1032,28 +1046,66 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 
 		private synchronized void setBootstrapped() {
+			boolean wasBootstrapped = bootstrapped;
 			bootstrapped = true;
-			callback.pluginStateChanged(getState());
+			if (!wasBootstrapped) callback.pluginStateChanged(getState());
 		}
 
-		private synchronized boolean getAndSetCircuitBuilt(boolean built) {
-			boolean old = circuitBuilt;
+		/**
+		 * Sets the `circuitBuilt` flag and returns true if the flag has
+		 * changed.
+		 */
+		private synchronized boolean setCircuitBuilt(boolean built) {
+			if (built == circuitBuilt) return false; // Unchanged
 			circuitBuilt = built;
-			if (built != old) callback.pluginStateChanged(getState());
-			return old;
+			callback.pluginStateChanged(getState());
+			return true; // Changed
 		}
 
-		private synchronized void enableNetwork(boolean enable) {
+		/**
+		 * Sets the `networkEnabled` flag and returns true if the flag has
+		 * changed.
+		 */
+		private synchronized boolean enableNetwork(boolean enable) {
+			boolean wasInitialised = networkInitialised;
+			boolean wasEnabled = networkEnabled;
 			networkInitialised = true;
 			networkEnabled = enable;
 			if (!enable) circuitBuilt = false;
-			callback.pluginStateChanged(getState());
+			if (!wasInitialised || enable != wasEnabled) {
+				callback.pluginStateChanged(getState());
+			}
+			return enable != wasEnabled;
 		}
 
-		private synchronized void setReasonsDisabled(int reasonsDisabled) {
+		/**
+		 * Sets the `paddingEnabled` flag and returns true if the flag has
+		 * changed. Doesn't affect getState().
+		 */
+		private synchronized boolean enableConnectionPadding(boolean enable) {
+			if (enable == paddingEnabled) return false; // Unchanged
+			paddingEnabled = enable;
+			return true; // Changed
+		}
+
+		/**
+		 * Sets the `ipv6Enabled` flag and returns true if the flag has
+		 * changed. Doesn't affect getState().
+		 */
+		private synchronized boolean enableIpv6(boolean enable) {
+			if (enable == ipv6Enabled) return false; // Unchanged
+			ipv6Enabled = enable;
+			return true; // Changed
+		}
+
+		private synchronized void setReasonsDisabled(int reasons) {
+			boolean wasChecked = settingsChecked;
 			settingsChecked = true;
-			this.reasonsDisabled = reasonsDisabled;
-			callback.pluginStateChanged(getState());
+			int oldReasons = reasonsDisabled;
+			reasonsDisabled = reasons;
+			if (!wasChecked || reasons != oldReasons) {
+				callback.pluginStateChanged(getState());
+			}
 		}
 
 		// Doesn't affect getState()
@@ -1068,6 +1120,17 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (serverSocket == ss) serverSocket = null;
 		}
 
+		/**
+		 * Sets the list of bridge types being used and returns true if the
+		 * list has changed. The list is empty if bridges are disabled.
+		 * Doesn't affect getState().
+		 */
+		private synchronized boolean setBridgeTypes(List<BridgeType> types) {
+			if (types.equals(bridgeTypes)) return false; // Unchanged
+			bridgeTypes = types;
+			return true; // Changed
+		}
+
 		private synchronized State getState() {
 			if (!started || stopped || !settingsChecked) {
 				return STARTING_STOPPING;

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -50,6 +50,7 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
+import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.SUPPORTED_VERSIONS;
@@ -235,8 +236,10 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			generateOffer();
 		} else if (e instanceof GroupVisibilityUpdatedEvent) {
 			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
-			if (g.getAffectedContacts().contains(contactId))
+			if (g.getVisibility() == SHARED &&
+					g.getAffectedContacts().contains(contactId)) {
 				generateOffer();
+			}
 		} else if (e instanceof MessageRequestedEvent) {
 			if (((MessageRequestedEvent) e).getContactId().equals(contactId))
 				generateBatch();
@@ -310,7 +313,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 							Collection<Message> batch =
 									db.generateRequestedBatch(txn, contactId,
 											BATCH_CAPACITY, maxLatency);
-							setNextSendTime(db.getNextSendTime(txn, contactId));
+							setNextSendTime(db.getNextSendTime(txn, contactId,
+									maxLatency));
 							return batch;
 						});
 				if (LOG.isLoggable(INFO))
@@ -353,7 +357,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 				Offer o = db.transactionWithNullableResult(false, txn -> {
 					Offer offer = db.generateOffer(txn, contactId,
 							MAX_MESSAGE_IDS, maxLatency);
-					setNextSendTime(db.getNextSendTime(txn, contactId));
+					setNextSendTime(db.getNextSendTime(txn, contactId,
+							maxLatency));
 					return offer;
 				});
 				if (LOG.isLoggable(INFO))

bramble-core/src/main/java/org/briarproject/bramble/sync/MailboxOutgoingSession.java

@@ -7,9 +7,9 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.sync.Ack;
-import org.briarproject.bramble.api.sync.DeferredSendHandler;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
@@ -29,7 +29,7 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LEN
 
 /**
  * A {@link SimplexOutgoingSession} for sending and acking messages via a
- * mailbox. The session uses a {@link DeferredSendHandler} to record the IDs
+ * mailbox. The session uses a {@link OutgoingSessionRecord} to record the IDs
  * of the messages sent and acked during the session so that they can be
  * recorded in the DB as sent or acked after the file has been successfully
  * uploaded to the mailbox.
@@ -41,7 +41,7 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 	private static final Logger LOG =
 			getLogger(MailboxOutgoingSession.class.getName());
 
-	private final DeferredSendHandler deferredSendHandler;
+	private final OutgoingSessionRecord sessionRecord;
 	private final long initialCapacity;
 
 	MailboxOutgoingSession(DatabaseComponent db,
@@ -51,11 +51,11 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 			long maxLatency,
 			StreamWriter streamWriter,
 			SyncRecordWriter recordWriter,
-			DeferredSendHandler deferredSendHandler,
+			OutgoingSessionRecord sessionRecord,
 			long capacity) {
 		super(db, eventBus, contactId, transportId, maxLatency, streamWriter,
 				recordWriter);
-		this.deferredSendHandler = deferredSendHandler;
+		this.sessionRecord = sessionRecord;
 		this.initialCapacity = capacity;
 	}
 
@@ -65,7 +65,7 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 			Collection<MessageId> idsToAck = loadMessageIdsToAck();
 			if (idsToAck.isEmpty()) break;
 			recordWriter.writeAck(new Ack(idsToAck));
-			deferredSendHandler.onAckSent(idsToAck);
+			sessionRecord.onAckSent(idsToAck);
 			LOG.info("Sent ack");
 		}
 	}
@@ -96,7 +96,7 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 					db.getMessageToSend(txn, contactId, m, maxLatency, false));
 			if (message == null) continue; // No longer shared
 			recordWriter.writeMessage(message);
-			deferredSendHandler.onMessageSent(m);
+			sessionRecord.onMessageSent(m);
 			LOG.info("Sent message");
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncSessionFactoryImpl.java

@@ -6,6 +6,7 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.PriorityHandler;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
@@ -25,6 +26,8 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_FILE_PAYLOAD_BYTES;
+
 @Immutable
 @NotNullByDefault
 class SyncSessionFactoryImpl implements SyncSessionFactory {
@@ -73,6 +76,18 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 		}
 	}
 
+	@Override
+	public SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
+			long maxLatency, StreamWriter streamWriter,
+			OutgoingSessionRecord sessionRecord) {
+		OutputStream out = streamWriter.getOutputStream();
+		SyncRecordWriter recordWriter =
+				recordWriterFactory.createRecordWriter(out);
+		return new MailboxOutgoingSession(db, eventBus, c, t, maxLatency,
+				streamWriter, recordWriter, sessionRecord,
+				MAX_FILE_PAYLOAD_BYTES);
+	}
+
 	@Override
 	public SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, int maxIdleTime, StreamWriter streamWriter,

bramble-core/src/main/resources/bridges

@@ -15,16 +15,19 @@ n Bridge obfs4 46.226.107.197:10300 A38FD6BDFD902882F5F5B9B7CCC95602A20B0BC4 cer
 n Bridge obfs4 185.181.11.86:443 A961609729E7FDF520B4E81F1F1B8FA1045285C3 cert=e5faG9Zk4Ni+e7z2YgGfevyKPQlMvkVGi4ublSsHYjaBovKeNXpOhbeFxzbZZoAzxAoGUQ iat-mode=0
 n Bridge obfs4 85.242.211.221:8042 A36A938DD7FDB8BACC846BA326EE0BA0D89A9252 cert=1AN6Pt1eFca3Y/WYD2TGAU3Al9cO4eouXE9SX63s66Z/ks3tVmgQ5GeXi1B5DOvx6Il7Zw iat-mode=0
 n Bridge obfs4 74.104.165.202:9002 EF432018A6AA5D970B2F84E39CD30A147030141C cert=PhppfUusY85dHGvWtGTybZ1fED4DtbHmALkNMIOIYrAz1B4xN7/2a5gyiZe1epju1BOHVg iat-mode=0
-n Bridge obfs4 70.34.242.31:443 7F026956402CDFF4BCBA8E11EE9C50E3FE0A2B72 cert=hP/KU7JATSfWH3HwS5Er/YLT0J+bRO3+s2fWx2yirrgf37EyrWvm/BQshoNje8WfUm6CBw iat-mode=0
 n Bridge obfs4 93.95.226.151:41185 460B0CFFC0CF1D965F3DE064E08BA1915E7C916A cert=inluPzp5Jp5OzZar1eQb4dcQ/YlAj/v0kHAUCoCr3rmLt03+pVuVTjoH4mRy4+acXpn+Gw iat-mode=0
 n Bridge obfs4 120.29.217.52:5223 40FE3DB9800272F9CDC76422F8ED7883280EE96D cert=/71PS4l8c/XJ4DIItlH9xMqNvPFg2RUTrHvPlQWh48u5et8h/yyyjCcYphUadDsfBWpaGQ iat-mode=0
-n Bridge obfs4 83.97.179.29:1199 D83068BFAA28E71DB024B786E1E803BE14257127 cert=IduGtt05tM59Xmvo0oVNWgIRgY4OGPJjFP+y2oa6RMDHQBL/GRyFOOgX70iiazNAIJNkPw iat-mode=0
-n Bridge obfs4 207.181.244.13:40132 37FE8D782F5DD2BAEEDAAB8257B701344676B6DD cert=f5Hbfn3ToMzH170cV8DfLly3vRynveidfOfDcbradIDtbLDX15V2yQ8eEH2CPKQJmQR2Hg iat-mode=0
 n Bridge obfs4 76.255.201.112:8888 96CF36C2ECCFB7376AB6BE905BECD2C2AE8AEFCD cert=+q0pjaiM0JMqHL/BKqCRD+pjflaw/S406eUDF7CnFgamvQW3l2HVLJhQ6uX9P8zff0PLGg iat-mode=0
 n Bridge obfs4 65.108.159.114:14174 E1AD374BA9F34BD98862D128AC54D40C7DC138AE cert=YMkxMSBN2OOd99AkJpFaEUyKkdqZgJt9oVJEgO1QnT37n/Vc2yR4nhx4k4VkPLfEP1f4eg iat-mode=0
 n Bridge obfs4 185.177.207.138:8443 53716FE26F23C8C6A71A2BC5D9D8DC64747278C7 cert=6jcYVilMEzxdsWghSrQFpYYJlkkir/GPIXw/EnddUK3S8ToVpMG8u1SwMOEdEs735RrMHw iat-mode=0
 n Bridge obfs4 176.123.2.253:1933 B855D141CE6C4DE0F7EA4AAED83EBA8373FA8191 cert=1rOoSaRagc6PPR//paIl+ukv1N+xWKCdBXMFxK0k/moEwH0lk5bURBrUDzIX35fVzaiicQ iat-mode=0
+n Bridge obfs4 5.252.176.61:9418 3E61130100AD827AB9CB33DAC052D9BC49A39509 cert=/aMyBPnKbQFISithD3i1KHUdpWeMpWG3SvUpq1YWCf2EQohFxQfw+646gW1knm4BI/DLRA iat-mode=0
+n Bridge obfs4 202.61.224.111:6902 A4F91299763DB925AE3BD29A0FC1A9821E5D9BAE cert=NBKm2MJ83wMvYShkqpD5RrbDtW5YpIZrFNnMw7Dj1XOM3plU60Bh4eziaQXe8fGtb8ZqKg iat-mode=0
+n Bridge obfs4 87.121.72.109:9002 C8081D4731C953FA4AE166946E72B29153351E34 cert=bikAqxKV6Ch5gFCBTdPI28VeShYa1ZgkLmvc7YZNLWFsFZoaCULL/3AQKjpIfvSiJs5jGQ iat-mode=0
+n Bridge obfs4 172.104.17.96:17900 B6B37AC96E163D0A5ECE55826D17B50B70F0A7F8 cert=gUz7svhPxoALgeN4lMYrXK7NBnaDqwu6SKRJOhaO9IIMBpnB8UhMCMKzzMho3b0RxWzBVg iat-mode=0
+n Bridge obfs4 70.34.249.113:443 F441B16ABB1055794C2CE01821FC05047B2C8CFC cert=MauLNoyq8EwjY4Qe0oASYzs2hXdSjNgy+BtP9oo1naHhRsyKTtAZzeNv08RnzWjMJrTwcg iat-mode=0
 v Bridge 135.181.113.164:54444 74AF4CCA614C454B7D3E81FF8BACD78CEBC7D7DE
 v Bridge 92.243.15.235:9001 477EAD3C04036B48235F1F27FC91420A286A4B7F
 v Bridge 77.96.91.103:443 ED000A75B79A58F1D83A4D1675C2A9395B71BE8E
-m Bridge meek_lite 192.0.2.2:2 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com
+v Bridge 213.108.108.145:17674 A39C0FE47963B6E8CFE9815549864DE544935A31
+m Bridge meek_lite 192.0.2.2:2 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com

bramble-core/src/test/java/org/briarproject/bramble/connection/ConnectionRegistryImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.connection;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.connection.InterruptibleConnection;
 import org.briarproject.bramble.api.contact.ContactId;
@@ -57,6 +58,10 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 	private final Priority high =
 			new Priority(fromHexString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"));
 
+	public ConnectionRegistryImplTest() throws FormatException {
+		// required for throws declaration
+	}
+
 	@Test
 	public void testRegisterMultipleConnections() {
 		context.checking(new Expectations() {{

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactManagerImplTest.java

@@ -17,7 +17,6 @@ import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
-import org.junit.Before;
 import org.junit.Test;
 
 import java.util.Collection;
@@ -63,13 +62,9 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	private final long timestamp = System.currentTimeMillis();
 	private final boolean alice = new Random().nextBoolean();
 
-	private ContactManagerImpl contactManager;
-
-	@Before
-	public void setUp() {
-		contactManager = new ContactManagerImpl(db, keyManager,
-				identityManager, pendingContactFactory);
-	}
+	private final ContactManagerImpl contactManager =
+			new ContactManagerImpl(db, keyManager, identityManager,
+					pendingContactFactory);
 
 	@Test
 	public void testAddContact() throws Exception {

bramble-core/src/test/java/org/briarproject/bramble/crypto/Blake2bDigestTest.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.crypto;
 
 import org.bouncycastle.crypto.digests.Blake2bDigest;
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
 import org.junit.Test;
@@ -47,7 +48,7 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	};
 
 	@Test
-	public void testDigestWithKeyedTestVectors() {
+	public void testDigestWithKeyedTestVectors() throws FormatException {
 		for (String[] keyedTestVector : KEYED_TEST_VECTORS) {
 			byte[] input = StringUtils.fromHexString(keyedTestVector[0]);
 			byte[] key = StringUtils.fromHexString(keyedTestVector[1]);
@@ -63,7 +64,8 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testDigestWithKeyedTestVectorsAndRandomUpdate() {
+	public void testDigestWithKeyedTestVectorsAndRandomUpdate()
+			throws FormatException {
 		Random random = new Random();
 		for (int i = 0; i < 100; i++) {
 			for (String[] keyedTestVector : KEYED_TEST_VECTORS) {
@@ -138,7 +140,7 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void runSelfTest() {
+	public void runSelfTest() throws FormatException {
 		Blake2bDigest testDigest = new Blake2bDigest(256);
 		byte[] md = new byte[64];
 

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
@@ -83,7 +84,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testRfc7748TestVector() {
+	public void testRfc7748TestVector() throws FormatException {
 		byte[] aPriv = parsePrivateKey(ALICE_PRIVATE);
 		byte[] aPub = fromHexString(ALICE_PUBLIC);
 		byte[] bPriv = parsePrivateKey(BOB_PRIVATE);
@@ -97,7 +98,8 @@ public class KeyAgreementTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testDerivesSameSharedSecretFromEquivalentPublicKey() {
+	public void testDerivesSameSharedSecretFromEquivalentPublicKey()
+			throws FormatException {
 		byte[] aPub = fromHexString(ALICE_PUBLIC);
 		byte[] bPriv = parsePrivateKey(BOB_PRIVATE);
 		byte[] sharedSecret = fromHexString(SHARED_SECRET);
@@ -168,7 +170,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 		return crypto.deriveSharedSecret(label, publicKey, keyPair, inputs);
 	}
 
-	private byte[] parsePrivateKey(String hex) {
+	private byte[] parsePrivateKey(String hex) throws FormatException {
 		// Private keys need to be clamped because curve25519-java does the
 		// clamping at key generation time, not multiplication time
 		return AgreementKeyParser.clamp(fromHexString(hex));

bramble-core/src/test/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipherTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
@@ -15,11 +16,11 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 
 	// Test vectors from the NaCl paper
 	// http://cr.yp.to/highspeed/naclcrypto-20090310.pdf
-	private static final byte[] TEST_KEY = StringUtils.fromHexString(
+	private final byte[] TEST_KEY = StringUtils.fromHexString(
 			"1b27556473e985d462cd51197a9a46c76009549eac6474f206c4ee0844f68389");
-	private static final byte[] TEST_IV = StringUtils.fromHexString(
+	private final byte[] TEST_IV = StringUtils.fromHexString(
 			"69696ee955b62b73cd62bda875fc73d68219e0036b7a0b37");
-	private static final byte[] TEST_PLAINTEXT = StringUtils.fromHexString(
+	private final byte[] TEST_PLAINTEXT = StringUtils.fromHexString(
 					"be075fc53c81f2d5cf141316" +
 					"ebeb0c7b5228c52a4c62cbd4" +
 					"4b66849b64244ffce5ecbaaf" +
@@ -31,7 +32,7 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 					"048977eb48f59ffd4924ca1c" +
 					"60902e52f0a089bc76897040" +
 					"e082f937763848645e0705");
-	private static final byte[] TEST_CIPHERTEXT = StringUtils.fromHexString(
+	private final byte[] TEST_CIPHERTEXT = StringUtils.fromHexString(
 					"f3ffc7703f9400e52a7dfb4b" +
 					"3d3305d98e993b9f48681273" +
 					"c29650ba32fc76ce48332ea7" +
@@ -46,6 +47,10 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 					"a43d14a6599b1f654cb45a74" +
 					"e355a5");
 
+	public XSalsa20Poly1305AuthenticatedCipherTest() throws FormatException {
+		// required for throws declaration
+	}
+
 	@Test
 	public void testEncrypt() throws Exception {
 		SecretKey k = new SecretKey(TEST_KEY);

bramble-core/src/test/java/org/briarproject/bramble/data/BdfReaderImplTest.java

@@ -618,11 +618,12 @@ public class BdfReaderImplTest extends BrambleTestCase {
 		r.readDictionary();
 	}
 
-	private void setContents(String hex) {
+	private void setContents(String hex) throws FormatException {
 		setContents(hex, DEFAULT_MAX_BUFFER_SIZE);
 	}
 
-	private void setContents(String hex, int maxBufferSize) {
+	private void setContents(String hex, int maxBufferSize)
+			throws FormatException {
 		ByteArrayInputStream in = new ByteArrayInputStream(fromHexString(hex));
 		r = new BdfReaderImpl(in, DEFAULT_NESTED_LIMIT, maxBufferSize);
 	}

bramble-core/src/test/java/org/briarproject/bramble/data/BdfWriterImplTest.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.data;
 
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
-import org.junit.Before;
 import org.junit.Test;
 
 import java.io.ByteArrayOutputStream;
@@ -17,14 +16,8 @@ import static org.junit.Assert.assertArrayEquals;
 
 public class BdfWriterImplTest extends BrambleTestCase {
 
-	private ByteArrayOutputStream out = null;
-	private BdfWriterImpl w = null;
-
-	@Before
-	public void setUp() {
-		out = new ByteArrayOutputStream();
-		w = new BdfWriterImpl(out);
-	}
+	private final ByteArrayOutputStream out = new ByteArrayOutputStream();
+	private final BdfWriterImpl w = new BdfWriterImpl(out);
 
 	@Test
 	public void testWriteNull() throws IOException {

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -303,11 +303,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the contact is in the DB (which it's not)
-			exactly(25).of(database).startTransaction();
+			exactly(27).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(25).of(database).containsContact(txn, contactId);
+			exactly(27).of(database).containsContact(txn, contactId);
 			will(returnValue(false));
-			exactly(25).of(database).abortTransaction(txn);
+			exactly(27).of(database).abortTransaction(txn);
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -321,6 +321,23 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// Expected
 		}
 
+		try {
+			db.transaction(true, transaction ->
+					db.containsAcksToSend(transaction, contactId));
+			fail();
+		} catch (NoSuchContactException expected) {
+			// Expected
+		}
+
+		try {
+			db.transaction(true, transaction ->
+					db.containsMessagesToSend(transaction, contactId,
+							123, true));
+			fail();
+		} catch (NoSuchContactException expected) {
+			// Expected
+		}
+
 		try {
 			db.transaction(false, transaction ->
 					db.generateAck(transaction, contactId, 123));

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -378,9 +378,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Initially there should be nothing to send
 		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
 		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
 
 		// Add some messages to ack
 		Message message1 = getMessage(groupId);
@@ -389,10 +389,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message1, DELIVERED, true, false, contactId);
 
 		// Both message IDs should be returned
-		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
-		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+		assertTrue(db.containsAcksToSend(txn, contactId));
 		Collection<MessageId> ids = db.getMessagesToAck(txn, contactId, 1234);
 		assertEquals(asList(messageId, messageId1), ids);
 
@@ -400,10 +397,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.lowerAckFlag(txn, contactId, asList(messageId, messageId1));
 
 		// No message IDs should be returned
-		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
-		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+		assertFalse(db.containsAcksToSend(txn, contactId));
 		assertEquals(emptyList(), db.getMessagesToAck(txn, contactId, 1234));
 
 		// Raise the ack flag again
@@ -411,10 +405,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.raiseAckFlag(txn, contactId, messageId1);
 
 		// Both message IDs should be returned
-		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
-		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+		assertTrue(db.containsAcksToSend(txn, contactId));
 		ids = db.getMessagesToAck(txn, contactId, 1234);
 		assertEquals(asList(messageId, messageId1), ids);
 
@@ -2029,37 +2020,51 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, UNKNOWN, false, false, null);
 
 		// There should be no messages to send
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Share the group with the contact - still no messages to send
 		db.addGroupVisibility(txn, contactId, groupId, true);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Set the message's state to DELIVERED - still no messages to send
 		db.setMessageState(txn, messageId, DELIVERED);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Share the message - now it should be sendable immediately
 		db.setMessageShared(txn, messageId, true);
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Mark the message as requested - it should still be sendable
 		db.raiseRequestedFlag(txn, contactId, messageId);
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Update the message's expiry time as though we sent it - now the
 		// message should be sendable after one round-trip
-		db.updateRetransmissionData(txn, contactId, messageId, 1000);
-		assertEquals(now + 2000, db.getNextSendTime(txn, contactId));
+		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+
+		// The message should be sendable immediately over a transport with
+		// lower latency
+		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
 
 		// Update the message's expiry time again - now it should be sendable
 		// after two round-trips
-		db.updateRetransmissionData(txn, contactId, messageId, 1000);
-		assertEquals(now + 4000, db.getNextSendTime(txn, contactId));
+		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
+		assertEquals(now + MAX_LATENCY * 4,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+
+		// The message should be sendable immediately over a transport with
+		// lower latency
+		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
 
 		// Delete the message - there should be no messages to send
 		db.deleteMessage(txn, messageId);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		db.commitTransaction(txn);
 		db.close();
@@ -2124,7 +2129,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2167,7 +2173,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// The message should not be sendable via the same transport
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
@@ -2214,7 +2221,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2225,8 +2233,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		// Reset the retransmission times
 		db.resetUnackedMessagesToSend(txn, contactId);
 
-		// The message should have infinitely short expiry
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		// The message should be sendable immediately
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// The message should be sendable
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
@@ -2579,7 +2587,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertNothingToSendLazily(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
 		Collection<MessageId> ids =
 				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
@@ -2590,7 +2598,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertOneMessageToSendLazily(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
 		Collection<MessageId> ids =
 				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
@@ -2601,7 +2609,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertNothingToSendEagerly(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertFalse(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
 		Collection<MessageId> unacked =
 				db.getUnackedMessagesToSend(txn, contactId);
 		assertTrue(unacked.isEmpty());
@@ -2611,7 +2619,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertOneMessageToSendEagerly(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertTrue(
-				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
 		Collection<MessageId> unacked =
 				db.getUnackedMessagesToSend(txn, contactId);
 		assertEquals(singletonList(messageId), unacked);

bramble-core/src/test/java/org/briarproject/bramble/identity/IdentityManagerImplTest.java

@@ -14,7 +14,6 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
-import org.junit.Before;
 import org.junit.Test;
 
 import static java.util.Collections.singletonList;
@@ -41,13 +40,8 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 	private final KeyPair handshakeKeyPair =
 			new KeyPair(handshakePublicKey, handshakePrivateKey);
 
-	private IdentityManagerImpl identityManager;
-
-	@Before
-	public void setUp() {
-		identityManager =
-				new IdentityManagerImpl(db, crypto, authorFactory, clock);
-	}
+	private final IdentityManagerImpl identityManager =
+			new IdentityManagerImpl(db, crypto, authorFactory, clock);
 
 	@Test
 	public void testOpenDatabaseIdentityRegistered() throws Exception {

bramble-core/src/test/java/org/briarproject/bramble/lifecycle/LifecycleManagerImplTest.java

@@ -5,20 +5,18 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager.OpenDatabaseHook;
+import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
-import org.junit.Before;
 import org.junit.Test;
 
-import java.util.concurrent.atomic.AtomicBoolean;
-
-import static junit.framework.TestCase.assertTrue;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
+import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPED;
+import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.ALREADY_RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.CLOCK_ERROR;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.SUCCESS;
 import static org.briarproject.bramble.api.system.Clock.MAX_REASONABLE_TIME_MS;
@@ -31,22 +29,18 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
 	private final EventBus eventBus = context.mock(EventBus.class);
 	private final Clock clock = context.mock(Clock.class);
+	private final OpenDatabaseHook hook = context.mock(OpenDatabaseHook.class);
+	private final Service service = context.mock(Service.class);
 
 	private final SecretKey dbKey = getSecretKey();
 
-	private LifecycleManagerImpl lifecycleManager;
-
-	@Before
-	public void setUp() {
-		lifecycleManager = new LifecycleManagerImpl(db, eventBus, clock);
-	}
+	private final LifecycleManagerImpl lifecycleManager =
+			new LifecycleManagerImpl(db, eventBus, clock);
 
 	@Test
 	public void testOpenDatabaseHooksAreCalledAtStartup() throws Exception {
 		long now = System.currentTimeMillis();
 		Transaction txn = new Transaction(null, false);
-		AtomicBoolean called = new AtomicBoolean(false);
-		OpenDatabaseHook hook = transaction -> called.set(true);
 
 		context.checking(new DbExpectations() {{
 			oneOf(clock).currentTimeMillis();
@@ -55,6 +49,7 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(false));
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(db).removeTemporaryMessages(txn);
+			oneOf(hook).onDatabaseOpened(txn);
 			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
 		}});
 
@@ -62,7 +57,38 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 
 		assertEquals(SUCCESS, lifecycleManager.startServices(dbKey));
 		assertEquals(RUNNING, lifecycleManager.getLifecycleState());
-		assertTrue(called.get());
+	}
+
+	@Test
+	public void testServicesAreStartedAndStopped() throws Exception {
+		long now = System.currentTimeMillis();
+		Transaction txn = new Transaction(null, false);
+
+		context.checking(new DbExpectations() {{
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(db).open(dbKey, lifecycleManager);
+			will(returnValue(false));
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
+			oneOf(db).removeTemporaryMessages(txn);
+			oneOf(service).startService();
+			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
+		}});
+
+		lifecycleManager.registerService(service);
+
+		assertEquals(SUCCESS, lifecycleManager.startServices(dbKey));
+		assertEquals(RUNNING, lifecycleManager.getLifecycleState());
+		context.assertIsSatisfied();
+
+		context.checking(new Expectations() {{
+			oneOf(db).close();
+			oneOf(service).stopService();
+			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
+		}});
+
+		lifecycleManager.stopServices();
+		assertEquals(STOPPED, lifecycleManager.getLifecycleState());
 	}
 
 	@Test
@@ -89,6 +115,31 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 		assertEquals(STARTING, lifecycleManager.getLifecycleState());
 	}
 
+	@Test
+	public void testSecondCallToStartServicesReturnsEarly() throws Exception {
+		long now = System.currentTimeMillis();
+		Transaction txn = new Transaction(null, false);
+
+		context.checking(new DbExpectations() {{
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(db).open(dbKey, lifecycleManager);
+			will(returnValue(false));
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
+			oneOf(db).removeTemporaryMessages(txn);
+			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
+		}});
+
+		assertEquals(SUCCESS, lifecycleManager.startServices(dbKey));
+		assertEquals(RUNNING, lifecycleManager.getLifecycleState());
+		context.assertIsSatisfied();
+
+		// Calling startServices() again should not try to open the DB or
+		// start the services again
+		assertEquals(ALREADY_RUNNING, lifecycleManager.startServices(dbKey));
+		assertEquals(RUNNING, lifecycleManager.getLifecycleState());
+	}
+
 	@Test
 	public void testSecondCallToStopServicesReturnsEarly() throws Exception {
 		long now = System.currentTimeMillis();
@@ -101,7 +152,7 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(false));
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(db).removeTemporaryMessages(txn);
-			exactly(2).of(eventBus).broadcast(with(any(LifecycleEvent.class)));
+			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
 		}});
 
 		assertEquals(SUCCESS, lifecycleManager.startServices(dbKey));
@@ -109,17 +160,17 @@ public class LifecycleManagerImplTest extends BrambleMockTestCase {
 		context.assertIsSatisfied();
 
 		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(LifecycleEvent.class)));
 			oneOf(db).close();
+			allowing(eventBus).broadcast(with(any(LifecycleEvent.class)));
 		}});
 
 		lifecycleManager.stopServices();
-		assertEquals(STOPPING, lifecycleManager.getLifecycleState());
+		assertEquals(STOPPED, lifecycleManager.getLifecycleState());
 		context.assertIsSatisfied();
 
 		// Calling stopServices() again should not broadcast another event or
 		// try to close the DB again
 		lifecycleManager.stopServices();
-		assertEquals(STOPPING, lifecycleManager.getLifecycleState());
+		assertEquals(STOPPED, lifecycleManager.getLifecycleState());
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ConnectivityCheckerImplTest.java

@@ -187,6 +187,32 @@ public class ConnectivityCheckerImplTest extends BrambleMockTestCase {
 		checker.onConnectivityCheckSucceeded(now);
 	}
 
+	@Test
+	public void testCheckIsCancelledWhenObserverIsRemoved() {
+		ConnectivityCheckerImpl checker = createChecker();
+
+		// When checkConnectivity() is called a check should be started
+		context.checking(new Expectations() {{
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(mailboxApiCaller).retryWithBackoff(apiCall);
+			will(returnValue(task));
+		}});
+
+		checker.checkConnectivity(properties, observer1);
+
+		// When the observer is removed the check should be cancelled
+		context.checking(new Expectations() {{
+			oneOf(task).cancel();
+		}});
+
+		checker.removeObserver(observer1);
+
+		// If the check runs anyway (cancellation came too late) the observer
+		// should not be called
+		checker.onConnectivityCheckSucceeded(now);
+	}
+
 	private ConnectivityCheckerImpl createChecker() {
 
 		return new ConnectivityCheckerImpl(clock, mailboxApiCaller) {

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ContactMailboxClientTest.java

@@ -0,0 +1,131 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+
+public class ContactMailboxClientTest extends BrambleMockTestCase {
+
+	private final MailboxWorkerFactory workerFactory =
+			context.mock(MailboxWorkerFactory.class);
+	private final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	private final TorReachabilityMonitor reachabilityMonitor =
+			context.mock(TorReachabilityMonitor.class);
+	private final MailboxWorker uploadWorker =
+			context.mock(MailboxWorker.class, "uploadWorker");
+	private final MailboxWorker downloadWorker =
+			context.mock(MailboxWorker.class, "downloadWorker");
+
+	private final MailboxProperties properties =
+			getMailboxProperties(false, CLIENT_SUPPORTS);
+	private final MailboxFolderId inboxId =
+			requireNonNull(properties.getInboxId());
+	private final MailboxFolderId outboxId =
+			requireNonNull(properties.getOutboxId());
+	private final ContactId contactId = getContactId();
+
+	private final ContactMailboxClient client =
+			new ContactMailboxClient(workerFactory, connectivityChecker,
+					reachabilityMonitor);
+
+	@Test
+	public void testStartAndDestroyWithNoContactsAssigned() {
+		client.start();
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignContactForUploadAndDestroyClient() {
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateAndStartUploadWorker();
+		client.assignContactForUpload(contactId, properties, outboxId);
+
+		// When the client is destroyed, the worker should be destroyed
+		expectDestroyWorker(uploadWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignAndDeassignContactForUpload() {
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateAndStartUploadWorker();
+		client.assignContactForUpload(contactId, properties, outboxId);
+
+		// When the contact is deassigned, the worker should be destroyed
+		expectDestroyWorker(uploadWorker);
+		client.deassignContactForUpload(contactId);
+		context.assertIsSatisfied();
+
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignContactForDownloadAndDestroyClient() {
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateAndStartDownloadWorker();
+		client.assignContactForDownload(contactId, properties, inboxId);
+
+		// When the client is destroyed, the worker should be destroyed
+		expectDestroyWorker(downloadWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignAndDeassignContactForDownload() {
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateAndStartDownloadWorker();
+		client.assignContactForDownload(contactId, properties, inboxId);
+
+		// When the contact is deassigned, the worker should be destroyed
+		expectDestroyWorker(downloadWorker);
+		client.deassignContactForDownload(contactId);
+		context.assertIsSatisfied();
+
+		client.destroy();
+	}
+
+	private void expectCreateAndStartUploadWorker() {
+		context.checking(new Expectations() {{
+			oneOf(workerFactory).createUploadWorker(connectivityChecker,
+					properties, outboxId, contactId);
+			will(returnValue(uploadWorker));
+			oneOf(uploadWorker).start();
+		}});
+	}
+
+	private void expectCreateAndStartDownloadWorker() {
+		context.checking(new Expectations() {{
+			oneOf(workerFactory).createDownloadWorkerForContactMailbox(
+					connectivityChecker, reachabilityMonitor, properties);
+			will(returnValue(downloadWorker));
+			oneOf(downloadWorker).start();
+		}});
+	}
+
+	private void expectDestroyWorker(MailboxWorker worker) {
+		context.checking(new Expectations() {{
+			oneOf(worker).destroy();
+		}});
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ContactMailboxDownloadWorkerTest.java

@@ -0,0 +1,136 @@
+package org.briarproject.bramble.mailbox;
+
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Collections.emptyList;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.junit.Assert.assertFalse;
+
+public class ContactMailboxDownloadWorkerTest
+		extends MailboxDownloadWorkerTest<ContactMailboxDownloadWorker> {
+
+	public ContactMailboxDownloadWorkerTest() {
+		mailboxProperties = getMailboxProperties(false, CLIENT_SUPPORTS);
+		worker = new ContactMailboxDownloadWorker(connectivityChecker,
+				torReachabilityMonitor, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, mailboxProperties);
+	}
+
+	@Test
+	public void testChecksConnectivityWhenStartedAndRemovesObserverWhenDestroyed() {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+
+	@Test
+	public void testChecksForFilesWhenConnectivityCheckSucceeds()
+			throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the connectivity check succeeds, a list-inbox task should be
+		// started for the first download cycle
+		AtomicReference<ApiCall> listTask = new AtomicReference<>();
+		expectStartTask(listTask);
+		worker.onConnectivityCheckSucceeded();
+
+		// When the list-inbox tasks runs and finds no files to download,
+		// it should add a Tor reachability observer
+		expectCheckForFiles(mailboxProperties.getInboxId(), emptyList());
+		expectAddReachabilityObserver();
+		assertFalse(listTask.get().callApi());
+
+		// When the reachability observer is called, a list-inbox task should
+		// be started for the second download cycle
+		expectStartTask(listTask);
+		worker.onTorReachable();
+
+		// When the list-inbox tasks runs and finds no files to download,
+		// it should finish the second download cycle
+		expectCheckForFiles(mailboxProperties.getInboxId(), emptyList());
+		assertFalse(listTask.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+
+	@Test
+	public void testDownloadsFilesWhenConnectivityCheckSucceeds()
+			throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the connectivity check succeeds, a list-inbox task should be
+		// started for the first download cycle
+		AtomicReference<ApiCall> listTask = new AtomicReference<>();
+		expectStartTask(listTask);
+		worker.onConnectivityCheckSucceeded();
+
+		// When the list-inbox tasks runs and finds some files to download,
+		// it should start a download task for the first file
+		AtomicReference<ApiCall> downloadTask = new AtomicReference<>();
+		expectCheckForFiles(mailboxProperties.getInboxId(), files);
+		expectStartTask(downloadTask);
+		assertFalse(listTask.get().callApi());
+
+		// When the first download task runs it should download the file to the
+		// location provided by the file manager and start a delete task
+		AtomicReference<ApiCall> deleteTask = new AtomicReference<>();
+		expectDownloadFile(mailboxProperties.getInboxId(), file1);
+		expectStartTask(deleteTask);
+		assertFalse(downloadTask.get().callApi());
+
+		// When the first delete task runs it should delete the file, ignore
+		// the tolerable failure, and start a download task for the next file
+		expectDeleteFile(mailboxProperties.getInboxId(), file1, true);
+		expectStartTask(downloadTask);
+		assertFalse(deleteTask.get().callApi());
+
+		// When the second download task runs it should download the file to
+		// the location provided by the file manager and start a delete task
+		expectDownloadFile(mailboxProperties.getInboxId(), file2);
+		expectStartTask(deleteTask);
+		assertFalse(downloadTask.get().callApi());
+
+		// When the second delete task runs it should delete the file and
+		// start a list-inbox task to check for files that may have arrived
+		// since the first download cycle started
+		expectDeleteFile(mailboxProperties.getInboxId(), file2, false);
+		expectStartTask(listTask);
+		assertFalse(deleteTask.get().callApi());
+
+		// When the list-inbox tasks runs and finds no more files to download,
+		// it should add a Tor reachability observer
+		expectCheckForFiles(mailboxProperties.getInboxId(), emptyList());
+		expectAddReachabilityObserver();
+		assertFalse(listTask.get().callApi());
+
+		// When the reachability observer is called, a list-inbox task should
+		// be started for the second download cycle
+		expectStartTask(listTask);
+		worker.onTorReachable();
+
+		// When the list-inbox tasks runs and finds no more files to download,
+		// it should finish the second download cycle
+		expectCheckForFiles(mailboxProperties.getInboxId(), emptyList());
+		assertFalse(listTask.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxApiIntegrationTest.java

@@ -1,8 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
-import org.briarproject.bramble.api.WeakSingletonProvider;
 import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.mailbox.InvalidMailboxIdException;
 import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFileId;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
@@ -13,7 +11,6 @@ import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
 import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.junit.AfterClass;
-import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Rule;
 import org.junit.Test;
@@ -25,14 +22,11 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import javax.annotation.Nonnull;
-import javax.net.SocketFactory;
-
-import okhttp3.OkHttpClient;
-
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.mailbox.MailboxIntegrationTestUtils.SETUP_TOKEN;
+import static org.briarproject.bramble.mailbox.MailboxIntegrationTestUtils.URL_BASE;
+import static org.briarproject.bramble.mailbox.MailboxIntegrationTestUtils.createMailboxApi;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.isOptionalTestEnabled;
@@ -40,56 +34,31 @@ import static org.briarproject.bramble.test.TestUtils.readBytes;
 import static org.briarproject.bramble.test.TestUtils.writeBytes;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeTrue;
 
-public class MailboxIntegrationTest extends BrambleTestCase {
+public class MailboxApiIntegrationTest extends BrambleTestCase {
 
 	@Rule
 	public TemporaryFolder folder = new TemporaryFolder();
 
-	private final static String URL_BASE = "http://127.0.0.1:8000";
-	private final static MailboxAuthToken SETUP_TOKEN;
+	private static final MailboxApi api = createMailboxApi();
 
-	static {
-		try {
-			SETUP_TOKEN = MailboxAuthToken.fromString(
-					"54686973206973206120736574757020746f6b656e20666f722042726961722e");
-		} catch (InvalidMailboxIdException e) {
-			throw new IllegalStateException();
-		}
-	}
-
-	private static final OkHttpClient client = new OkHttpClient.Builder()
-			.socketFactory(SocketFactory.getDefault())
-			.connectTimeout(60_000, MILLISECONDS)
-			.build();
-	private static final WeakSingletonProvider<OkHttpClient>
-			httpClientProvider =
-			new WeakSingletonProvider<OkHttpClient>() {
-				@Override
-				@Nonnull
-				public OkHttpClient createInstance() {
-					return client;
-				}
-			};
-	private final static MailboxApiImpl api =
-			new MailboxApiImpl(httpClientProvider);
 	// needs to be static to keep values across different tests
 	private static MailboxProperties ownerProperties;
 
 	/**
 	 * Called before each test to make sure the mailbox is setup once
 	 * before starting with individual tests.
-	 * {@link BeforeClass} needs to be static, so we can't use the API class.
 	 */
-	@Before
-	public void ensureSetup() throws IOException, ApiException {
+	@BeforeClass
+	public static void setUp() throws IOException, ApiException {
 		// Skip this test unless it's explicitly enabled in the environment
-		assumeTrue(isOptionalTestEnabled(MailboxIntegrationTest.class));
+		assumeTrue(isOptionalTestEnabled(MailboxApiIntegrationTest.class));
 
-		if (ownerProperties != null) return;
+		assertNull(ownerProperties);
 		MailboxProperties setupProperties = new MailboxProperties(
 				URL_BASE, SETUP_TOKEN, new ArrayList<>());
 		ownerProperties = api.setup(setupProperties);
@@ -98,7 +67,7 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 	@AfterClass
 	// we can't test wiping as a regular test as it stops the mailbox
 	public static void wipe() throws IOException, ApiException {
-		if (!isOptionalTestEnabled(MailboxIntegrationTest.class)) return;
+		if (!isOptionalTestEnabled(MailboxApiIntegrationTest.class)) return;
 
 		api.wipeMailbox(ownerProperties);
 
@@ -121,7 +90,7 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 		ContactId contactId = new ContactId(1);
 		MailboxContact contact = getMailboxContact(contactId);
 		MailboxProperties contactProperties = new MailboxProperties(
-				ownerProperties.getBaseUrl(), contact.token,
+				ownerProperties.getOnion(), contact.token,
 				new ArrayList<>(), contact.inboxId, contact.outboxId);
 		api.addContact(ownerProperties, contact);
 
@@ -167,7 +136,7 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 		ContactId contactId = new ContactId(1);
 		MailboxContact contact = getMailboxContact(contactId);
 		MailboxProperties contactProperties = new MailboxProperties(
-				ownerProperties.getBaseUrl(), contact.token,
+				ownerProperties.getOnion(), contact.token,
 				new ArrayList<>(), contact.inboxId, contact.outboxId);
 		api.addContact(ownerProperties, contact);
 
@@ -184,7 +153,7 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 		MailboxFileId fileName1 = files1.get(0).name;
 
 		// owner can't check files
-		assertThrows(ApiException.class, () ->
+		assertThrows(TolerableFailureException.class, () ->
 				api.getFiles(ownerProperties, contact.inboxId));
 
 		// contact downloads file
@@ -195,12 +164,13 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 
 		// owner can't download file, even if knowing name
 		File file1forbidden = folder.newFile();
-		assertThrows(ApiException.class, () -> api.getFile(ownerProperties,
-				contact.inboxId, fileName1, file1forbidden));
+		assertThrows(TolerableFailureException.class, () ->
+				api.getFile(ownerProperties, contact.inboxId, fileName1,
+						file1forbidden));
 		assertEquals(0, file1forbidden.length());
 
 		// owner can't delete file
-		assertThrows(ApiException.class, () ->
+		assertThrows(TolerableFailureException.class, () ->
 				api.deleteFile(ownerProperties, contact.inboxId, fileName1));
 
 		// contact deletes file
@@ -230,7 +200,7 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 		MailboxFileId file3name = files2.get(1).name;
 
 		// contact can't list files in contact's outbox
-		assertThrows(ApiException.class, () ->
+		assertThrows(TolerableFailureException.class, () ->
 				api.getFiles(contactProperties, contact.outboxId));
 
 		// owner downloads both files from contact's outbox
@@ -250,17 +220,19 @@ public class MailboxIntegrationTest extends BrambleTestCase {
 		// contact can't download files again, even if knowing name
 		File file2forbidden = folder.newFile();
 		File file3forbidden = folder.newFile();
-		assertThrows(ApiException.class, () -> api.getFile(contactProperties,
-				contact.outboxId, file2name, file2forbidden));
-		assertThrows(ApiException.class, () -> api.getFile(contactProperties,
-				contact.outboxId, file3name, file3forbidden));
+		assertThrows(TolerableFailureException.class, () ->
+				api.getFile(contactProperties, contact.outboxId, file2name,
+						file2forbidden));
+		assertThrows(TolerableFailureException.class, () ->
+				api.getFile(contactProperties, contact.outboxId, file3name,
+						file3forbidden));
 		assertEquals(0, file1forbidden.length());
 		assertEquals(0, file2forbidden.length());
 
 		// contact can't delete files in outbox
-		assertThrows(ApiException.class, () ->
+		assertThrows(TolerableFailureException.class, () ->
 				api.deleteFile(contactProperties, contact.outboxId, file2name));
-		assertThrows(ApiException.class, () ->
+		assertThrows(TolerableFailureException.class, () ->
 				api.deleteFile(contactProperties, contact.outboxId, file3name));
 
 		// owner deletes files

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxApiTest.java

@@ -68,7 +68,10 @@ public class MailboxApiTest extends BrambleTestCase {
 					return client;
 				}
 			};
-	private final MailboxApiImpl api = new MailboxApiImpl(httpClientProvider);
+	// We aren't using a real onion address, so use the given address verbatim
+	private final UrlConverter urlConverter = onion -> onion;
+	private final MailboxApiImpl api = new MailboxApiImpl(httpClientProvider,
+			urlConverter);
 
 	private final MailboxAuthToken token = new MailboxAuthToken(getRandomId());
 	private final MailboxAuthToken token2 = new MailboxAuthToken(getRandomId());
@@ -627,6 +630,7 @@ public class MailboxApiTest extends BrambleTestCase {
 		server.enqueue(new MockResponse().setBody(invalidResponse3));
 		server.enqueue(new MockResponse().setBody(invalidResponse4));
 		server.enqueue(new MockResponse().setResponseCode(401));
+		server.enqueue(new MockResponse().setResponseCode(404));
 		server.enqueue(new MockResponse().setResponseCode(500));
 		server.start();
 		String baseUrl = getBaseUrl(server);
@@ -703,13 +707,21 @@ public class MailboxApiTest extends BrambleTestCase {
 		assertEquals("GET", request8.getMethod());
 		assertToken(request8, token);
 
-		// 500 internal server error
-		assertThrows(ApiException.class,
-				() -> api.getFiles(properties, contactInboxId));
+		// 404 not found
+		assertThrows(TolerableFailureException.class, () ->
+				api.getFiles(properties, contactInboxId));
 		RecordedRequest request9 = server.takeRequest();
 		assertEquals("/files/" + contactInboxId, request9.getPath());
 		assertEquals("GET", request9.getMethod());
 		assertToken(request9, token);
+
+		// 500 internal server error
+		assertThrows(ApiException.class,
+				() -> api.getFiles(properties, contactInboxId));
+		RecordedRequest request10 = server.takeRequest();
+		assertEquals("/files/" + contactInboxId, request10.getPath());
+		assertEquals("GET", request10.getMethod());
+		assertToken(request10, token);
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxDownloadWorkerTest.java

@@ -0,0 +1,130 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.mailbox.MailboxFileId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.jmock.Expectations;
+import org.jmock.lib.action.DoAllAction;
+import org.junit.After;
+import org.junit.Before;
+
+import java.io.File;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Arrays.asList;
+import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
+
+abstract class MailboxDownloadWorkerTest<W extends MailboxDownloadWorker>
+		extends BrambleMockTestCase {
+
+	final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	final TorReachabilityMonitor torReachabilityMonitor =
+			context.mock(TorReachabilityMonitor.class);
+	final MailboxApiCaller mailboxApiCaller =
+			context.mock(MailboxApiCaller.class);
+	final MailboxApi mailboxApi = context.mock(MailboxApi.class);
+	final MailboxFileManager mailboxFileManager =
+			context.mock(MailboxFileManager.class);
+	private final Cancellable apiCall = context.mock(Cancellable.class);
+
+	private final long now = System.currentTimeMillis();
+	final MailboxFile file1 =
+			new MailboxFile(new MailboxFileId(getRandomId()), now - 1);
+	final MailboxFile file2 =
+			new MailboxFile(new MailboxFileId(getRandomId()), now);
+	final List<MailboxFile> files = asList(file1, file2);
+
+	private File testDir, tempFile;
+	MailboxProperties mailboxProperties;
+	W worker;
+
+	@Before
+	public void setUp() {
+		testDir = getTestDirectory();
+		tempFile = new File(testDir, "temp");
+	}
+
+	@After
+	public void tearDown() {
+		deleteTestDirectory(testDir);
+	}
+
+
+	void expectStartConnectivityCheck() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).checkConnectivity(
+					with(mailboxProperties), with(worker));
+		}});
+	}
+
+	void expectStartTask(AtomicReference<ApiCall> task) {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(task, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+	}
+
+	void expectCheckForFoldersWithAvailableFiles(
+			List<MailboxFolderId> folderIds) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).getFolders(mailboxProperties);
+			will(returnValue(folderIds));
+		}});
+	}
+
+	void expectCheckForFiles(MailboxFolderId folderId,
+			List<MailboxFile> files) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).getFiles(mailboxProperties, folderId);
+			will(returnValue(files));
+		}});
+	}
+
+	void expectDownloadFile(MailboxFolderId folderId,
+			MailboxFile file)
+			throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createTempFileForDownload();
+			will(returnValue(tempFile));
+			oneOf(mailboxApi).getFile(mailboxProperties, folderId, file.name,
+					tempFile);
+			oneOf(mailboxFileManager).handleDownloadedFile(tempFile);
+		}});
+	}
+
+	void expectDeleteFile(MailboxFolderId folderId, MailboxFile file,
+			boolean tolerableFailure) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).deleteFile(mailboxProperties, folderId,
+					file.name);
+			if (tolerableFailure) {
+				will(throwException(new TolerableFailureException()));
+			}
+		}});
+	}
+
+	void expectAddReachabilityObserver() {
+		context.checking(new Expectations() {{
+			oneOf(torReachabilityMonitor).addOneShotObserver(worker);
+		}});
+	}
+
+	void expectRemoveObservers() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).removeObserver(worker);
+			oneOf(torReachabilityMonitor).removeObserver(worker);
+		}});
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxFileManagerImplTest.java

@@ -2,16 +2,20 @@ package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.connection.ConnectionManager.TagController;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.briarproject.bramble.test.ConsumeArgumentAction;
 import org.briarproject.bramble.test.RunAction;
 import org.jmock.Expectations;
 import org.jmock.lib.action.DoAllAction;
@@ -20,6 +24,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -28,11 +33,14 @@ import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleS
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
 import static org.briarproject.bramble.api.plugin.file.FileConstants.PROP_PATH;
 import static org.briarproject.bramble.mailbox.MailboxFileManagerImpl.DOWNLOAD_DIR_NAME;
+import static org.briarproject.bramble.mailbox.MailboxFileManagerImpl.UPLOAD_DIR_NAME;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 
@@ -47,6 +55,10 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 	private final SimplexPlugin plugin = context.mock(SimplexPlugin.class);
 	private final TransportConnectionReader transportConnectionReader =
 			context.mock(TransportConnectionReader.class);
+	private final TransportConnectionWriter transportConnectionWriter =
+			context.mock(TransportConnectionWriter.class);
+
+	private final ContactId contactId = getContactId();
 
 	private File mailboxDir;
 	private MailboxFileManagerImpl manager;
@@ -65,17 +77,25 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testHandlesOrphanedFilesAtStartup() throws Exception {
-		// Create an orphaned file, left behind at the previous shutdown
+		// Create an orphaned upload, left behind at the previous shutdown
+		File uploadDir = new File(mailboxDir, UPLOAD_DIR_NAME);
+		//noinspection ResultOfMethodCallIgnored
+		uploadDir.mkdirs();
+		File orphanedUpload = new File(uploadDir, "orphan");
+		assertTrue(orphanedUpload.createNewFile());
+
+		// Create an orphaned download, left behind at the previous shutdown
 		File downloadDir = new File(mailboxDir, DOWNLOAD_DIR_NAME);
 		//noinspection ResultOfMethodCallIgnored
 		downloadDir.mkdirs();
-		File orphan = new File(downloadDir, "orphan");
-		assertTrue(orphan.createNewFile());
+		File orphanedDownload = new File(downloadDir, "orphan");
+		assertTrue(orphanedDownload.createNewFile());
 
 		TransportProperties props = new TransportProperties();
-		props.put(PROP_PATH, orphan.getAbsolutePath());
+		props.put(PROP_PATH, orphanedDownload.getAbsolutePath());
 
-		// When the plugin becomes active the orphaned file should be handled
+		// When the plugin becomes active the orphaned upload should be deleted
+		// and the orphaned download should be handled
 		context.checking(new Expectations() {{
 			oneOf(ioExecutor).execute(with(any(Runnable.class)));
 			will(new RunAction());
@@ -90,10 +110,12 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		assertFalse(orphanedUpload.exists());
 	}
 
 	@Test
-	public void testDeletesFileWhenReadSucceeds() throws Exception {
+	public void testDeletesDownloadedFileWhenReadSucceeds() throws Exception {
 		expectCheckForOrphans();
 		manager.eventOccurred(new TransportActiveEvent(ID));
 
@@ -102,7 +124,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 				new AtomicReference<>(null);
 		AtomicReference<TagController> controller = new AtomicReference<>(null);
 
-		expectPassFileToConnectionManager(f, reader, controller);
+		expectPassDownloadedFileToConnectionManager(f, reader, controller);
 		manager.handleDownloadedFile(f);
 
 		// The read is successful, so the tag controller should allow the tag
@@ -117,29 +139,117 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testDeletesFileWhenTagIsNotRecognised() throws Exception {
-		testDeletesFile(false, RUNNING, false);
-	}
-
-	@Test
-	public void testDeletesFileWhenReadFails() throws Exception {
-		testDeletesFile(true, RUNNING, false);
-	}
-
-	@Test
-	public void testDoesNotDeleteFileWhenTagIsNotRecognisedAtShutdown()
+	public void testDeletesDownloadedFileWhenTagIsNotRecognised()
 			throws Exception {
-		testDeletesFile(false, STOPPING, true);
+		testDeletesDownloadedFile(false, RUNNING, false);
 	}
 
 	@Test
-	public void testDoesNotDeleteFileWhenReadFailsAtShutdown()
-			throws Exception {
-		testDeletesFile(true, STOPPING, true);
+	public void testDeletesDownloadedFileWhenReadFails() throws Exception {
+		testDeletesDownloadedFile(true, RUNNING, false);
 	}
 
-	private void testDeletesFile(boolean recognised, LifecycleState state,
-			boolean fileExists) throws Exception {
+	@Test
+	public void testDoesNotDeleteDownloadedFileWhenTagIsNotRecognisedAtShutdown()
+			throws Exception {
+		testDeletesDownloadedFile(false, STOPPING, true);
+	}
+
+	@Test
+	public void testDoesNotDeleteDownloadedFileWhenReadFailsAtShutdown()
+			throws Exception {
+		testDeletesDownloadedFile(true, STOPPING, true);
+	}
+
+	@Test(expected = IOException.class)
+	public void testThrowsExceptionIfPluginFailsToCreateWriter()
+			throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(null));
+		}});
+
+		manager.createAndWriteTempFileForUpload(contactId, sessionRecord);
+	}
+
+	@Test(expected = IOException.class)
+	public void testThrowsExceptionIfSessionFailsWithException()
+			throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(transportConnectionWriter));
+			oneOf(transportConnectionWriter).dispose(true);
+			oneOf(connectionManager).manageOutgoingConnection(with(contactId),
+					with(ID), with(any(TransportConnectionWriter.class)),
+					with(sessionRecord));
+			// The session fails with an exception. We need to use an action
+			// for this, as createAndWriteTempFileForUpload() waits for it to
+			// happen before returning
+			will(new ConsumeArgumentAction<>(TransportConnectionWriter.class, 2,
+					writer -> {
+						try {
+							writer.dispose(true);
+						} catch (IOException e) {
+							fail();
+						}
+					}
+			));
+		}});
+
+		manager.createAndWriteTempFileForUpload(contactId, sessionRecord);
+	}
+
+	@Test
+	public void testReturnsFileIfSessionSucceeds() throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(transportConnectionWriter));
+			oneOf(transportConnectionWriter).dispose(false);
+			oneOf(connectionManager).manageOutgoingConnection(with(contactId),
+					with(ID), with(any(TransportConnectionWriter.class)),
+					with(sessionRecord));
+			// The session succeeds. We need to use an action for this, as
+			// createAndWriteTempFileForUpload() waits for it to happen before
+			// returning
+			will(new ConsumeArgumentAction<>(TransportConnectionWriter.class, 2,
+					writer -> {
+						try {
+							writer.dispose(false);
+						} catch (IOException e) {
+							fail();
+						}
+					}
+			));
+		}});
+
+		File f = manager.createAndWriteTempFileForUpload(contactId,
+				sessionRecord);
+		assertTrue(f.exists());
+	}
+
+	private void testDeletesDownloadedFile(boolean recognised,
+			LifecycleState state, boolean fileExists) throws Exception {
 		expectCheckForOrphans();
 		manager.eventOccurred(new TransportActiveEvent(ID));
 
@@ -148,7 +258,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 				new AtomicReference<>(null);
 		AtomicReference<TagController> controller = new AtomicReference<>(null);
 
-		expectPassFileToConnectionManager(f, reader, controller);
+		expectPassDownloadedFileToConnectionManager(f, reader, controller);
 		manager.handleDownloadedFile(f);
 
 		context.checking(new Expectations() {{
@@ -169,7 +279,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 		}});
 	}
 
-	private void expectPassFileToConnectionManager(File f,
+	private void expectPassDownloadedFileToConnectionManager(File f,
 			AtomicReference<TransportConnectionReader> reader,
 			AtomicReference<TagController> controller) {
 		TransportProperties props = new TransportProperties();

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxIntegrationTestComponent.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.BrambleCoreModule;
+import org.briarproject.bramble.test.BrambleCoreIntegrationTestModule;
+import org.briarproject.bramble.test.BrambleIntegrationTestComponent;
+
+import javax.inject.Singleton;
+
+import dagger.Component;
+
+@Singleton
+@Component(modules = {
+		BrambleCoreIntegrationTestModule.class,
+		BrambleCoreModule.class
+})
+interface MailboxIntegrationTestComponent extends
+		BrambleIntegrationTestComponent {
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxIntegrationTestUtils.java

@@ -0,0 +1,80 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.api.WeakSingletonProvider;
+import org.briarproject.bramble.api.mailbox.InvalidMailboxIdException;
+import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
+import org.briarproject.bramble.io.IoModule;
+
+import javax.annotation.Nonnull;
+import javax.inject.Singleton;
+import javax.net.SocketFactory;
+
+import dagger.Module;
+import dagger.Provides;
+import okhttp3.OkHttpClient;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+
+class MailboxIntegrationTestUtils {
+
+	static final String URL_BASE = "http://127.0.0.1:8000";
+	static final MailboxAuthToken SETUP_TOKEN;
+
+	static {
+		try {
+			SETUP_TOKEN = MailboxAuthToken.fromString(
+					"54686973206973206120736574757020746f6b656e20666f722042726961722e");
+		} catch (InvalidMailboxIdException e) {
+			throw new IllegalStateException();
+		}
+	}
+
+	static WeakSingletonProvider<OkHttpClient> createHttpClientProvider() {
+		OkHttpClient client = new OkHttpClient.Builder()
+				.socketFactory(SocketFactory.getDefault())
+				.connectTimeout(60_000, MILLISECONDS)
+				.build();
+		return new WeakSingletonProvider<OkHttpClient>() {
+			@Override
+			@Nonnull
+			public OkHttpClient createInstance() {
+				return client;
+			}
+		};
+	}
+
+	static MailboxApi createMailboxApi() {
+		return new MailboxApiImpl(createHttpClientProvider(), onion -> onion);
+	}
+
+	static MailboxIntegrationTestComponent createTestComponent() {
+		MailboxIntegrationTestComponent component =
+				DaggerMailboxIntegrationTestComponent
+						.builder()
+						.ioModule(new TestIoModule())
+						.mailboxModule(new TestMailboxModule())
+						.build();
+		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(component);
+		return component;
+	}
+
+	@Module
+	static class TestIoModule extends IoModule {
+
+		@Provides
+		@Singleton
+		WeakSingletonProvider<OkHttpClient> provideOkHttpClientProvider() {
+			return createHttpClientProvider();
+		}
+	}
+
+	@Module
+	static class TestMailboxModule extends MailboxModule {
+
+		@Provides
+		UrlConverter provideUrlConverter() {
+			return onion -> onion;
+		}
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxManagerImplTest.java

@@ -0,0 +1,128 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
+import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEvent;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Random;
+import java.util.concurrent.Executor;
+
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.hasEvent;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class MailboxManagerImplTest extends BrambleMockTestCase {
+
+	private final Executor ioExecutor = context.mock(Executor.class);
+	private final MailboxApi api = context.mock(MailboxApi.class);
+	private final TransactionManager db =
+			context.mock(TransactionManager.class);
+	private final MailboxSettingsManager mailboxSettingsManager =
+			context.mock(MailboxSettingsManager.class);
+	private final MailboxPairingTaskFactory pairingTaskFactory =
+			context.mock(MailboxPairingTaskFactory.class);
+	private final Clock clock =
+			context.mock(Clock.class);
+
+	private final MailboxManagerImpl manager = new MailboxManagerImpl(
+			ioExecutor, api, db, mailboxSettingsManager, pairingTaskFactory,
+			clock);
+
+	@Test
+	public void testDbExceptionDoesNotRecordFailure() throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(true),
+					withNullableDbCallable(txn));
+			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
+			will(throwException(new DbException()));
+		}});
+
+		assertFalse(manager.checkConnection());
+		assertFalse(hasEvent(txn, OwnMailboxConnectionStatusEvent.class));
+	}
+
+	@Test
+	public void testIOExceptionDoesRecordFailure() throws Exception {
+		Transaction txn = new Transaction(null, true);
+		Transaction txn2 = new Transaction(null, false);
+		MailboxProperties props = getMailboxProperties(true, CLIENT_SUPPORTS);
+		long now = new Random().nextLong();
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(true),
+					withNullableDbCallable(txn));
+			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
+			will(returnValue(props));
+			oneOf(api).getServerSupports(props);
+			will(throwException(new IOException()));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
+			oneOf(mailboxSettingsManager)
+					.recordFailedConnectionAttempt(txn2, now);
+		}});
+
+		assertFalse(manager.checkConnection());
+	}
+
+	@Test
+	public void testApiExceptionDoesRecordFailure() throws Exception {
+		Transaction txn = new Transaction(null, true);
+		Transaction txn2 = new Transaction(null, false);
+		MailboxProperties props = getMailboxProperties(true, CLIENT_SUPPORTS);
+		long now = new Random().nextLong();
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(true),
+					withNullableDbCallable(txn));
+			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
+			will(returnValue(props));
+			oneOf(api).getServerSupports(props);
+			will(throwException(new MailboxApi.ApiException()));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
+			oneOf(mailboxSettingsManager)
+					.recordFailedConnectionAttempt(txn2, now);
+		}});
+
+		assertFalse(manager.checkConnection());
+	}
+
+	@Test
+	public void testConnectionSuccess() throws Exception {
+		Transaction txn = new Transaction(null, true);
+		Transaction txn2 = new Transaction(null, false);
+		MailboxProperties props = getMailboxProperties(true, CLIENT_SUPPORTS);
+		long now = new Random().nextLong();
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(true),
+					withNullableDbCallable(txn));
+			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
+			will(returnValue(props));
+			oneOf(api).getServerSupports(props);
+			will(returnValue(CLIENT_SUPPORTS));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
+			oneOf(mailboxSettingsManager)
+					.recordSuccessfulConnection(txn2, now, CLIENT_SUPPORTS);
+		}});
+
+		assertTrue(manager.checkConnection());
+	}
+
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImplTest.java

@@ -13,7 +13,6 @@ import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
-import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
@@ -33,7 +32,6 @@ import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.test.TestUtils.hasEvent;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -57,7 +55,6 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 
 	private final String onion = getRandomString(56);
 	private final byte[] onionBytes = getRandomBytes(32);
-	private final String baseUrl = "http://" + onion + ".onion"; // TODO
 	private final MailboxAuthToken setupToken =
 			new MailboxAuthToken(getRandomId());
 	private final MailboxAuthToken ownerToken =
@@ -65,9 +62,9 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 	private final String validPayload = getValidPayload();
 	private final long time = System.currentTimeMillis();
 	private final MailboxProperties setupProperties = new MailboxProperties(
-			baseUrl, setupToken, new ArrayList<>());
+			onion, setupToken, new ArrayList<>());
 	private final MailboxProperties ownerProperties = new MailboxProperties(
-			baseUrl, ownerToken, new ArrayList<>());
+			onion, ownerToken, new ArrayList<>());
 
 	@Test
 	public void testInitialQrCodeReceivedState() {
@@ -138,7 +135,6 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 			i.getAndIncrement();
 		});
 		task.run();
-		hasEvent(txn, OwnMailboxConnectionStatusEvent.class);
 	}
 
 	@Test
@@ -210,7 +206,7 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 	private PredicateMatcher<MailboxProperties> matches(MailboxProperties p2) {
 		return new PredicateMatcher<>(MailboxProperties.class, p1 ->
 				p1.getAuthToken().equals(p2.getAuthToken()) &&
-						p1.getBaseUrl().equals(p2.getBaseUrl()) &&
+						p1.getOnion().equals(p2.getOnion()) &&
 						p1.isOwner() == p2.isOwner() &&
 						p1.getServerSupports().equals(p2.getServerSupports()));
 	}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImplTest.java

@@ -18,6 +18,7 @@ import java.util.List;
 import java.util.Random;
 
 import static java.util.Arrays.asList;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.mailbox.MailboxSettingsManagerImpl.SETTINGS_KEY_ATTEMPTS;
 import static org.briarproject.bramble.mailbox.MailboxSettingsManagerImpl.SETTINGS_KEY_LAST_ATTEMPT;
 import static org.briarproject.bramble.mailbox.MailboxSettingsManagerImpl.SETTINGS_KEY_LAST_SUCCESS;
@@ -83,7 +84,7 @@ public class MailboxSettingsManagerImplTest extends BrambleMockTestCase {
 
 		MailboxProperties properties = manager.getOwnMailboxProperties(txn);
 		assertNotNull(properties);
-		assertEquals(onion, properties.getBaseUrl());
+		assertEquals(onion, properties.getOnion());
 		assertEquals(token, properties.getAuthToken());
 		assertEquals(serverSupports, properties.getServerSupports());
 		assertTrue(properties.isOwner());
@@ -162,6 +163,28 @@ public class MailboxSettingsManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		manager.recordSuccessfulConnection(txn, now);
+		assertTrue(hasEvent(txn, OwnMailboxConnectionStatusEvent.class));
+	}
+
+	@Test
+	public void testRecordsSuccessWithVersions() throws Exception {
+		Transaction txn = new Transaction(null, false);
+		List<MailboxVersion> versions = singletonList(new MailboxVersion(2, 1));
+		Settings expectedSettings = new Settings();
+		expectedSettings.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
+		expectedSettings.putLong(SETTINGS_KEY_LAST_SUCCESS, now);
+		expectedSettings.putInt(SETTINGS_KEY_ATTEMPTS, 0);
+		expectedSettings.putInt(SETTINGS_KEY_SERVER_SUPPORTS, 0);
+		int[] newVersionsInts = {2, 1};
+		expectedSettings
+				.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, newVersionsInts);
+
+		context.checking(new Expectations() {{
+			oneOf(settingsManager).mergeSettings(txn, expectedSettings,
+					SETTINGS_NAMESPACE);
+		}});
+
+		manager.recordSuccessfulConnection(txn, now, versions);
 		hasEvent(txn, OwnMailboxConnectionStatusEvent.class);
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxUpdateManagerImplTest.java

@@ -109,7 +109,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 		updateNoMailbox = new MailboxUpdate(someClientSupportsList);
 
 		updateProps = getMailboxProperties(false, someServerSupportsList);
-		ownProps = new MailboxProperties(updateProps.getBaseUrl(),
+		ownProps = new MailboxProperties(updateProps.getOnion(),
 				updateProps.getAuthToken(), someServerSupportsList);
 		updateWithMailbox = new MailboxUpdateWithMailbox(someClientSupportsList,
 				updateProps);
@@ -170,7 +170,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					emptyServerSupports, emptyPropsDict, true);
+					emptyServerSupports, emptyPropsDict);
 
 			oneOf(clientHelper).mergeGroupMetadata(txn, localGroup.getId(),
 					sentDict);
@@ -225,7 +225,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					someServerSupports, propsDict, true);
+					someServerSupports, propsDict);
 
 			oneOf(clientHelper).mergeGroupMetadata(txn, localGroup.getId(),
 					sentDict);
@@ -276,7 +276,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(emptyMessageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					emptyServerSupports, emptyPropsDict, true);
+					emptyServerSupports, emptyPropsDict);
 
 			oneOf(clientHelper).mergeGroupMetadata(txn, localGroup.getId(),
 					sentDict);
@@ -341,7 +341,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(emptyMessageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					emptyServerSupports, emptyPropsDict, true);
+					emptyServerSupports, emptyPropsDict);
 
 			oneOf(clientHelper).mergeGroupMetadata(txn, localGroup.getId(),
 					sentDict);
@@ -400,7 +400,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 2,
-					newerClientSupports, someServerSupports, propsDict, true);
+					newerClientSupports, someServerSupports, propsDict);
 			oneOf(db).removeMessage(txn, messageId);
 
 			oneOf(clientHelper).mergeGroupMetadata(txn, localGroup.getId(),
@@ -441,7 +441,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					emptyServerSupports, emptyPropsDict, true);
+					emptyServerSupports, emptyPropsDict);
 		}});
 
 		MailboxUpdateManagerImpl t = createInstance(someClientSupportsList);
@@ -484,7 +484,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
-					someServerSupports, propsDict, true);
+					someServerSupports, propsDict);
 		}});
 
 		MailboxUpdateManagerImpl t = createInstance(someClientSupportsList);
@@ -674,7 +674,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 2, someClientSupports,
-					someServerSupports, propsDict, true);
+					someServerSupports, propsDict);
 			oneOf(db).removeMessage(txn, latestId);
 		}});
 
@@ -712,7 +712,7 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			expectStoreMessage(txn, contactGroup.getId(), 2, someClientSupports,
-					emptyServerSupports, emptyPropsDict, true);
+					emptyServerSupports, emptyPropsDict);
 			oneOf(db).removeMessage(txn, latestId);
 		}});
 
@@ -890,15 +890,14 @@ public class MailboxUpdateManagerImplTest extends BrambleMockTestCase {
 
 	private void expectStoreMessage(Transaction txn, GroupId g,
 			long version, BdfList clientSupports, BdfList serverSupports,
-			BdfDictionary properties, boolean local)
-			throws Exception {
+			BdfDictionary properties) throws Exception {
 		BdfList body = BdfList.of(version, clientSupports, serverSupports,
 				properties);
 		Message message = getMessage(g);
 		long timestamp = message.getTimestamp();
 		BdfDictionary meta = BdfDictionary.of(
 				new BdfEntry(MSG_KEY_VERSION, version),
-				new BdfEntry(MSG_KEY_LOCAL, local)
+				new BdfEntry(MSG_KEY_LOCAL, true)
 		);
 
 		context.checking(new Expectations() {{

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxUploadWorkerTest.java

@@ -0,0 +1,465 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
+import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.briarproject.bramble.test.ConsumeArgumentAction;
+import org.briarproject.bramble.test.DbExpectations;
+import org.briarproject.bramble.test.RunAction;
+import org.jmock.Expectations;
+import org.jmock.lib.action.DoAllAction;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Collections.singletonList;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
+import static org.briarproject.bramble.mailbox.MailboxUploadWorker.CHECK_DELAY_MS;
+import static org.briarproject.bramble.mailbox.MailboxUploadWorker.RETRY_DELAY_MS;
+import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class MailboxUploadWorkerTest extends BrambleMockTestCase {
+
+	private final Executor ioExecutor = context.mock(Executor.class);
+	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
+	private final Clock clock = context.mock(Clock.class);
+	private final TaskScheduler taskScheduler =
+			context.mock(TaskScheduler.class);
+	private final EventBus eventBus = context.mock(EventBus.class);
+	private final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	private final MailboxApiCaller mailboxApiCaller =
+			context.mock(MailboxApiCaller.class);
+	private final MailboxApi mailboxApi = context.mock(MailboxApi.class);
+	private final MailboxFileManager mailboxFileManager =
+			context.mock(MailboxFileManager.class);
+	private final Cancellable apiCall =
+			context.mock(Cancellable.class, "apiCall");
+	private final Cancellable wakeupTask =
+			context.mock(Cancellable.class, "wakeupTask");
+	private final Cancellable checkTask =
+			context.mock(Cancellable.class, "checkTask");
+
+	private final MailboxProperties mailboxProperties =
+			getMailboxProperties(false, CLIENT_SUPPORTS);
+	private final long now = System.currentTimeMillis();
+	private final MailboxFolderId folderId = new MailboxFolderId(getRandomId());
+	private final ContactId contactId = getContactId();
+	private final MessageId ackedId = new MessageId(getRandomId());
+	private final MessageId sentId = new MessageId(getRandomId());
+	private final MessageId newMessageId = new MessageId(getRandomId());
+
+	private File testDir, tempFile;
+	private MailboxUploadWorker worker;
+
+	@Before
+	public void setUp() {
+		testDir = getTestDirectory();
+		tempFile = new File(testDir, "temp");
+		worker = new MailboxUploadWorker(ioExecutor, db, clock, taskScheduler,
+				eventBus, connectivityChecker, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, mailboxProperties, folderId, contactId);
+	}
+
+	@After
+	public void tearDown() {
+		deleteTestDirectory(testDir);
+	}
+
+	@Test
+	public void testChecksForDataWhenStartedAndRemovesObserverWhenDestroyed()
+			throws Exception {
+		// When the worker is started it should check for data to send
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendNoDataWaiting();
+
+		worker.start();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testChecksConnectivityWhenStartedIfDataIsReady()
+			throws Exception {
+		Transaction recordTxn = new Transaction(null, false);
+
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// Create the temporary file so we can test that it gets deleted
+		assertTrue(testDir.mkdirs());
+		assertTrue(tempFile.createNewFile());
+
+		// When the connectivity check succeeds, the worker should write a file
+		// and start an upload task
+		expectRunTaskOnIoExecutor();
+		AtomicReference<ApiCall> upload = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(new DoAllAction(
+					// Record some IDs as acked and sent
+					new ConsumeArgumentAction<>(OutgoingSessionRecord.class, 1,
+							record -> {
+								record.onAckSent(singletonList(ackedId));
+								record.onMessageSent(sentId);
+							}),
+					returnValue(tempFile)
+			));
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(upload, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the upload task runs, it should upload the file, record
+		// the acked/sent messages in the DB, and check for more data to send
+		context.checking(new DbExpectations() {{
+			oneOf(mailboxApi).addFile(mailboxProperties, folderId, tempFile);
+			oneOf(db).transaction(with(false), withDbRunnable(recordTxn));
+			oneOf(db).setAckSent(recordTxn, contactId, singletonList(ackedId));
+			oneOf(db).setMessagesSent(recordTxn, contactId,
+					singletonList(sentId), MAX_LATENCY);
+		}});
+		expectCheckForDataToSendNoDataWaiting();
+
+		assertFalse(upload.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// The file should have been deleted
+		assertFalse(tempFile.exists());
+	}
+
+	@Test
+	public void testCancelsApiCallWhenDestroyed() throws Exception {
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// Create the temporary file so we can test that it gets deleted
+		assertTrue(testDir.mkdirs());
+		assertTrue(tempFile.createNewFile());
+
+		// When the connectivity check succeeds, the worker should write a file
+		// and start an upload task
+		expectRunTaskOnIoExecutor();
+		AtomicReference<ApiCall> upload = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(new DoAllAction(
+					// Record some IDs as acked and sent
+					new ConsumeArgumentAction<>(OutgoingSessionRecord.class, 1,
+							record -> {
+								record.onAckSent(singletonList(ackedId));
+								record.onMessageSent(sentId);
+							}),
+					returnValue(tempFile)
+			));
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(upload, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener and cancel the upload task
+		context.checking(new Expectations() {{
+			oneOf(apiCall).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// The file should have been deleted
+		assertFalse(tempFile.exists());
+
+		// If the upload task runs anyway (cancellation came too late), it
+		// should return early when it finds the state has changed
+		assertFalse(upload.get().callApi());
+	}
+
+	@Test
+	public void testSchedulesWakeupWhenStartedIfDataIsNotReady()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// When the wakeup task runs it should check for data to send
+		expectCheckForDataToSendNoDataWaiting();
+
+		wakeup.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testCancelsWakeupIfDestroyedBeforeWakingUp() throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// When the worker is destroyed it should cancel the wakeup and
+		// remove the connectivity observer and event listener
+		context.checking(new Expectations() {{
+			oneOf(wakeupTask).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// If the wakeup task runs anyway (cancellation came too late), it
+		// should return early without doing anything
+		wakeup.get().run();
+	}
+
+	@Test
+	public void testCancelsWakeupIfEventIsReceivedBeforeWakingUp()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// Before the wakeup task runs, the worker receives an event that
+		// indicates new data may be available. The worker should cancel the
+		// wakeup task and schedule a check for new data after a short delay
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		expectScheduleCheck(check, CHECK_DELAY_MS);
+		context.checking(new Expectations() {{
+			oneOf(wakeupTask).cancel();
+		}});
+
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// If the wakeup task runs anyway (cancellation came too late), it
+		// should return early when it finds the state has changed
+		wakeup.get().run();
+
+		// Before the check task runs, the worker receives another event that
+		// indicates new data may be available. The event should be ignored,
+		// as a check for new data has already been scheduled
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// When the check task runs, it should check for new data
+		expectCheckForDataToSendNoDataWaiting();
+
+		check.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testCancelsCheckWhenDestroyed() throws Exception {
+		// When the worker is started it should check for data to send
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendNoDataWaiting();
+
+		worker.start();
+
+		// The worker receives an event that indicates new data may be
+		// available. The worker should schedule a check for new data after
+		// a short delay
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		expectScheduleCheck(check, CHECK_DELAY_MS);
+
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// When the worker is destroyed it should cancel the check and
+		// remove the connectivity observer and event listener
+		context.checking(new Expectations() {{
+			oneOf(checkTask).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// If the check runs anyway (cancellation came too late), it should
+		// return early when it finds the state has changed
+		check.get().run();
+	}
+
+	@Test
+	public void testRetriesAfterDelayIfExceptionOccursWhileWritingFile()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should try to
+		// write a file. This fails with an exception, so the worker should
+		// retry by scheduling a check for new data after a short delay
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(throwException(new IOException())); // Oh noes!
+		}});
+		expectScheduleCheck(check, RETRY_DELAY_MS);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the check task runs it should check for new data
+		expectCheckForDataToSendNoDataWaiting();
+
+		check.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	private void expectRunTaskOnIoExecutor() {
+		context.checking(new Expectations() {{
+			oneOf(ioExecutor).execute(with(any(Runnable.class)));
+			will(new RunAction());
+		}});
+	}
+
+	private void expectCheckForDataToSendNoDataWaiting() throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(Long.MAX_VALUE)); // No data waiting
+		}});
+	}
+
+	private void expectCheckForDataToSendAndScheduleWakeup(
+			AtomicReference<Runnable> wakeup) throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(now + 1234L)); // Data waiting but not ready
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(taskScheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(1234L), with(MILLISECONDS));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(wakeup, Runnable.class, 0),
+					returnValue(wakeupTask)
+			));
+		}});
+	}
+
+	private void expectCheckForDataToSendAndStartConnectivityCheck()
+			throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(0L)); // Data ready to send
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(connectivityChecker).checkConnectivity(mailboxProperties,
+					worker);
+		}});
+	}
+
+	private void expectScheduleCheck(AtomicReference<Runnable> check,
+			long delay) {
+		context.checking(new Expectations() {{
+			oneOf(taskScheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(delay), with(MILLISECONDS));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(check, Runnable.class, 0),
+					returnValue(checkTask)
+			));
+		}});
+	}
+
+	private void expectRemoveObserverAndListener() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).removeObserver(worker);
+			oneOf(eventBus).removeListener(worker);
+		}});
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxClientTest.java

@@ -0,0 +1,208 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+
+public class OwnMailboxClientTest extends BrambleMockTestCase {
+
+	private final MailboxWorkerFactory workerFactory =
+			context.mock(MailboxWorkerFactory.class);
+	private final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	private final TorReachabilityMonitor reachabilityMonitor =
+			context.mock(TorReachabilityMonitor.class);
+	private final MailboxWorker contactListWorker =
+			context.mock(MailboxWorker.class, "contactListWorker");
+	private final MailboxWorker uploadWorker1 =
+			context.mock(MailboxWorker.class, "uploadWorker1");
+	private final MailboxWorker uploadWorker2 =
+			context.mock(MailboxWorker.class, "uploadWorker2");
+	private final MailboxWorker downloadWorker =
+			context.mock(MailboxWorker.class, "downloadWorker");
+
+	private final MailboxProperties properties =
+			getMailboxProperties(true, CLIENT_SUPPORTS);
+	private final MailboxFolderId folderId = new MailboxFolderId(getRandomId());
+	private final ContactId contactId1 = getContactId();
+	private final ContactId contactId2 = getContactId();
+
+	private final OwnMailboxClient client;
+
+	public OwnMailboxClientTest() {
+		expectCreateContactListWorker();
+		client = new OwnMailboxClient(workerFactory, connectivityChecker,
+				reachabilityMonitor, properties);
+		context.assertIsSatisfied();
+	}
+
+	@Test
+	public void testStartAndDestroyWithNoContactsAssigned() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignContactForUploadAndDestroyClient() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateUploadWorker(contactId1, uploadWorker1);
+		expectStartWorker(uploadWorker1);
+		client.assignContactForUpload(contactId1, properties, folderId);
+
+		// When the client is destroyed, the worker should be destroyed
+		expectDestroyWorker(uploadWorker1);
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignAndDeassignContactForUpload() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateUploadWorker(contactId1, uploadWorker1);
+		expectStartWorker(uploadWorker1);
+		client.assignContactForUpload(contactId1, properties, folderId);
+
+		// When the contact is deassigned, the worker should be destroyed
+		expectDestroyWorker(uploadWorker1);
+		client.deassignContactForUpload(contactId1);
+		context.assertIsSatisfied();
+
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignAndDeassignTwoContactsForUpload() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		// When the first contact is assigned, the first worker should be
+		// created and started
+		expectCreateUploadWorker(contactId1, uploadWorker1);
+		expectStartWorker(uploadWorker1);
+		client.assignContactForUpload(contactId1, properties, folderId);
+
+		// When the second contact is assigned, the second worker should be
+		// created and started
+		expectCreateUploadWorker(contactId2, uploadWorker2);
+		expectStartWorker(uploadWorker2);
+		client.assignContactForUpload(contactId2, properties, folderId);
+
+		// When the second contact is deassigned, the second worker should be
+		// destroyed
+		expectDestroyWorker(uploadWorker2);
+		client.deassignContactForUpload(contactId2);
+		context.assertIsSatisfied();
+
+		// When the first contact is deassigned, the first worker should be
+		// destroyed
+		expectDestroyWorker(uploadWorker1);
+		client.deassignContactForUpload(contactId1);
+		context.assertIsSatisfied();
+
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignContactForDownloadAndDestroyClient() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		// When the contact is assigned, the worker should be created and
+		// started
+		expectCreateDownloadWorker();
+		expectStartWorker(downloadWorker);
+		client.assignContactForDownload(contactId1, properties, folderId);
+
+		// When the client is destroyed, the worker should be destroyed
+		expectDestroyWorker(downloadWorker);
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	@Test
+	public void testAssignAndDeassignTwoContactsForDownload() {
+		expectStartWorker(contactListWorker);
+		client.start();
+
+		// When the first contact is assigned, the worker should be created and
+		// started
+		expectCreateDownloadWorker();
+		expectStartWorker(downloadWorker);
+		client.assignContactForDownload(contactId1, properties, folderId);
+
+		// When the second contact is assigned, nothing should happen to the
+		// worker
+		client.assignContactForDownload(contactId2, properties, folderId);
+
+		// When the first contact is deassigned, nothing should happen to the
+		// worker
+		client.deassignContactForDownload(contactId1);
+
+		// When the second contact is deassigned, the worker should be
+		// destroyed
+		expectDestroyWorker(downloadWorker);
+		client.deassignContactForDownload(contactId2);
+		context.assertIsSatisfied();
+
+		expectDestroyWorker(contactListWorker);
+		client.destroy();
+	}
+
+	private void expectCreateContactListWorker() {
+		context.checking(new Expectations() {{
+			oneOf(workerFactory).createContactListWorkerForOwnMailbox(
+					connectivityChecker, properties);
+			will(returnValue(contactListWorker));
+		}});
+	}
+
+	private void expectCreateUploadWorker(ContactId contactId,
+			MailboxWorker worker) {
+		context.checking(new Expectations() {{
+			oneOf(workerFactory).createUploadWorker(connectivityChecker,
+					properties, folderId, contactId);
+			will(returnValue(worker));
+		}});
+	}
+
+	private void expectCreateDownloadWorker() {
+		context.checking(new Expectations() {{
+			oneOf(workerFactory).createDownloadWorkerForOwnMailbox(
+					connectivityChecker, reachabilityMonitor, properties);
+			will(returnValue(downloadWorker));
+		}});
+	}
+
+	private void expectStartWorker(MailboxWorker worker) {
+		context.checking(new Expectations() {{
+			oneOf(worker).start();
+		}});
+	}
+
+	private void expectDestroyWorker(MailboxWorker worker) {
+		context.checking(new Expectations() {{
+			oneOf(worker).destroy();
+		}});
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxConnectivityCheckerTest.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
 import org.briarproject.bramble.test.BrambleMockTestCase;
@@ -15,8 +16,10 @@ import org.jmock.lib.action.DoAllAction;
 import org.junit.Test;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicReference;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
 import static org.junit.Assert.assertFalse;
@@ -39,6 +42,8 @@ public class OwnMailboxConnectivityCheckerTest extends BrambleMockTestCase {
 	private final MailboxProperties properties =
 			getMailboxProperties(true, CLIENT_SUPPORTS);
 	private final long now = System.currentTimeMillis();
+	private final List<MailboxVersion> serverSupports =
+			singletonList(new MailboxVersion(123, 456));
 
 	@Test
 	public void testObserverIsCalledWhenCheckSucceeds() throws Exception {
@@ -62,12 +67,13 @@ public class OwnMailboxConnectivityCheckerTest extends BrambleMockTestCase {
 		// When the check succeeds, the success should be recorded in the DB
 		// and the observer should be called
 		context.checking(new DbExpectations() {{
-			oneOf(mailboxApi).checkStatus(properties);
-			will(returnValue(true));
+			oneOf(mailboxApi).getServerSupports(properties);
+			will(returnValue(serverSupports));
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
-			oneOf(mailboxSettingsManager).recordSuccessfulConnection(txn, now);
+			oneOf(mailboxSettingsManager).recordSuccessfulConnection(txn, now,
+					serverSupports);
 			oneOf(observer).onConnectivityCheckSucceeded();
 		}});
 
@@ -97,7 +103,7 @@ public class OwnMailboxConnectivityCheckerTest extends BrambleMockTestCase {
 		// When the check fails, the failure should be recorded in the DB and
 		// the observer should not be called
 		context.checking(new DbExpectations() {{
-			oneOf(mailboxApi).checkStatus(properties);
+			oneOf(mailboxApi).getServerSupports(properties);
 			will(throwException(new IOException()));
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxContactListWorkerIntegrationTest.java

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.briarproject.bramble.mailbox.MailboxIntegrationTestUtils.createTestComponent;
+import static org.junit.Assert.assertTrue;
+
+public class OwnMailboxContactListWorkerIntegrationTest
+		extends BrambleTestCase {
+
+	private MailboxIntegrationTestComponent component;
+
+	@Before
+	public void setUp() {
+		component = createTestComponent();
+	}
+
+	// Just test that we can build the component. TODO: Write actual tests
+	@Test
+	public void testBuild() {
+		assertTrue(true);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxContactListWorkerTest.java

@@ -0,0 +1,406 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
+import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.NoSuchContactException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
+import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxContact;
+import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.briarproject.bramble.test.DbExpectations;
+import org.briarproject.bramble.test.RunAction;
+import org.jmock.Expectations;
+import org.jmock.lib.action.DoAllAction;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.test.TestUtils.getContact;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class OwnMailboxContactListWorkerTest extends BrambleMockTestCase {
+
+	private final Executor ioExecutor = context.mock(Executor.class);
+	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
+	private final EventBus eventBus = context.mock(EventBus.class);
+	private final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	private final MailboxApiCaller mailboxApiCaller =
+			context.mock(MailboxApiCaller.class);
+	private final MailboxApi mailboxApi = context.mock(MailboxApi.class);
+	private final MailboxUpdateManager mailboxUpdateManager =
+			context.mock(MailboxUpdateManager.class);
+	private final Cancellable apiCall = context.mock(Cancellable.class);
+
+	private final MailboxProperties mailboxProperties =
+			getMailboxProperties(true, CLIENT_SUPPORTS);
+	private final Contact contact1 = getContact(), contact2 = getContact();
+	private final MailboxProperties contactProperties1 =
+			getMailboxProperties(false, CLIENT_SUPPORTS);
+	private final MailboxProperties contactProperties2 =
+			getMailboxProperties(false, CLIENT_SUPPORTS);
+	private final MailboxUpdateWithMailbox update1 =
+			new MailboxUpdateWithMailbox(CLIENT_SUPPORTS, contactProperties1);
+	private final MailboxUpdateWithMailbox update2 =
+			new MailboxUpdateWithMailbox(CLIENT_SUPPORTS, contactProperties2);
+
+	private final OwnMailboxContactListWorker worker =
+			new OwnMailboxContactListWorker(ioExecutor, db, eventBus,
+					connectivityChecker, mailboxApiCaller, mailboxApi,
+					mailboxUpdateManager, mailboxProperties);
+
+	@Test
+	public void testChecksConnectivityWhenStartedAndRemovesObserverWhenDestroyed() {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+
+		worker.start();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveConnectivityObserverAndEventListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testUpdatesContactListWhenConnectivityCheckSucceeds()
+			throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should start a
+		// task to fetch the remote contact list
+		AtomicReference<ApiCall> fetchList = new AtomicReference<>();
+		expectStartTaskToFetchRemoteContactList(fetchList);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the fetch task runs it should fetch the remote contact list,
+		// load the local contact list, and find the differences. Contact 2
+		// needs to be added and contact 1 needs to be removed. The worker
+		// should load the mailbox update for contact 2 and start a task to
+		// add contact 2 to the mailbox
+		expectFetchRemoteContactList(singletonList(contact1.getId()));
+		expectRunTaskOnIoExecutor();
+		expectLoadLocalContactList(singletonList(contact2));
+		expectRunTaskOnIoExecutor();
+		expectLoadMailboxUpdate(contact2, update2);
+		AtomicReference<ApiCall> addContact = new AtomicReference<>();
+		expectStartTaskToAddContact(addContact);
+
+		assertFalse(fetchList.get().callApi());
+
+		// When the add-contact task runs it should add contact 2 to the
+		// mailbox, then continue with the next update
+		AtomicReference<MailboxContact> added = new AtomicReference<>();
+		expectAddContactToMailbox(added);
+		AtomicReference<ApiCall> removeContact = new AtomicReference<>();
+		expectStartTaskToRemoveContact(removeContact);
+
+		assertFalse(addContact.get().callApi());
+
+		// Check that the added contact has the expected properties
+		MailboxContact expected = new MailboxContact(contact2.getId(),
+				contactProperties2.getAuthToken(),
+				requireNonNull(contactProperties2.getInboxId()),
+				requireNonNull(contactProperties2.getOutboxId()));
+		assertMailboxContactEquals(expected, added.get());
+
+		// When the remove-contact task runs it should remove contact 1 from
+		// the mailbox
+		expectRemoveContactFromMailbox(contact1);
+
+		assertFalse(removeContact.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveConnectivityObserverAndEventListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testHandlesEventsAfterMakingInitialUpdates() throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should start a
+		// task to fetch the remote contact list
+		AtomicReference<ApiCall> fetchList = new AtomicReference<>();
+		expectStartTaskToFetchRemoteContactList(fetchList);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the fetch task runs it should fetch the remote contact list,
+		// load the local contact list, and find the differences. The lists
+		// are the same, so the worker should wait for changes
+		expectFetchRemoteContactList(emptyList());
+		expectRunTaskOnIoExecutor();
+		expectLoadLocalContactList(emptyList());
+
+		assertFalse(fetchList.get().callApi());
+
+		// When a contact is added, the worker should load the contact's
+		// mailbox update and start a task to add the contact to the mailbox
+		expectRunTaskOnIoExecutor();
+		expectLoadMailboxUpdate(contact1, update1);
+		AtomicReference<ApiCall> addContact = new AtomicReference<>();
+		expectStartTaskToAddContact(addContact);
+
+		worker.eventOccurred(new ContactAddedEvent(contact1.getId(), true));
+
+		// When the add-contact task runs it should add contact 1 to the
+		// mailbox
+		AtomicReference<MailboxContact> added = new AtomicReference<>();
+		expectAddContactToMailbox(added);
+
+		assertFalse(addContact.get().callApi());
+
+		// Check that the added contact has the expected properties
+		MailboxContact expected = new MailboxContact(contact1.getId(),
+				contactProperties1.getAuthToken(),
+				requireNonNull(contactProperties1.getInboxId()),
+				requireNonNull(contactProperties1.getOutboxId()));
+		assertMailboxContactEquals(expected, added.get());
+
+		// When the contact is removed again, the worker should start a task
+		// to remove the contact from the mailbox
+		expectRunTaskOnIoExecutor();
+		AtomicReference<ApiCall> removeContact = new AtomicReference<>();
+		expectStartTaskToRemoveContact(removeContact);
+
+		worker.eventOccurred(new ContactRemovedEvent(contact1.getId()));
+
+		// When the remove-contact task runs it should remove the contact from
+		// the mailbox
+		expectRemoveContactFromMailbox(contact1);
+
+		assertFalse(removeContact.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveConnectivityObserverAndEventListener();
+
+		worker.destroy();
+	}
+
+
+	@Test
+	public void testHandlesNoSuchContactException() throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should start a
+		// task to fetch the remote contact list
+		AtomicReference<ApiCall> fetchList = new AtomicReference<>();
+		expectStartTaskToFetchRemoteContactList(fetchList);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the fetch task runs it should fetch the remote contact list,
+		// load the local contact list, and find the differences. Contact 1
+		// needs to be added, so the worker should submit a task to the
+		// IO executor to load the contact's mailbox update
+		expectFetchRemoteContactList(emptyList());
+		expectRunTaskOnIoExecutor();
+		expectLoadLocalContactList(singletonList(contact1));
+		AtomicReference<Runnable> loadUpdate = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(ioExecutor).execute(with(any(Runnable.class)));
+			will(new CaptureArgumentAction<>(loadUpdate, Runnable.class, 0));
+		}});
+
+		assertFalse(fetchList.get().callApi());
+
+		// Before the contact's mailbox update can be loaded, the contact
+		// is removed
+		worker.eventOccurred(new ContactRemovedEvent(contact1.getId()));
+
+		// When the load-update task runs, a NoSuchContactException is thrown.
+		// The worker should abandon adding the contact and move on to the
+		// next update, which is the removal of the same contact. The worker
+		// should start a task to remove the contact from the mailbox
+		Transaction txn = new Transaction(null, false);
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
+			oneOf(mailboxUpdateManager).getLocalUpdate(txn, contact1.getId());
+			will(throwException(new NoSuchContactException()));
+		}});
+		AtomicReference<ApiCall> removeContact = new AtomicReference<>();
+		expectStartTaskToRemoveContact(removeContact);
+
+		loadUpdate.get().run();
+
+		// When the remove-contact task runs it should remove the contact from
+		// the mailbox. The contact was never added, so the call throws a
+		// TolerableFailureException
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).deleteContact(mailboxProperties,
+					contact1.getId());
+			will(throwException(new TolerableFailureException()));
+		}});
+
+		assertFalse(removeContact.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveConnectivityObserverAndEventListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testCancelsApiCallWhenDestroyed() {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should start a
+		// task to fetch the remote contact list
+		AtomicReference<ApiCall> fetchList = new AtomicReference<>();
+		expectStartTaskToFetchRemoteContactList(fetchList);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// The worker is destroyed before the task runs. The worker should
+		// cancel the task remove the connectivity observer and event listener
+		context.checking(new Expectations() {{
+			oneOf(apiCall).cancel();
+		}});
+		expectRemoveConnectivityObserverAndEventListener();
+
+		worker.destroy();
+	}
+
+	private void expectStartConnectivityCheck() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).checkConnectivity(
+					with(mailboxProperties), with(worker));
+		}});
+	}
+
+	private void expectRemoveConnectivityObserverAndEventListener() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).removeObserver(worker);
+			oneOf(eventBus).removeListener(worker);
+		}});
+	}
+
+	private void expectStartTaskToFetchRemoteContactList(
+			AtomicReference<ApiCall> task) {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(task, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+	}
+
+	private void expectFetchRemoteContactList(List<ContactId> remote)
+			throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).getContacts(mailboxProperties);
+			will(returnValue(remote));
+		}});
+	}
+
+	private void expectLoadLocalContactList(List<Contact> local)
+			throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).getContacts(txn);
+			will(returnValue(local));
+		}});
+	}
+
+	private void expectLoadMailboxUpdate(Contact c, MailboxUpdate update)
+			throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true),
+					withDbCallable(txn));
+			oneOf(mailboxUpdateManager).getLocalUpdate(txn, c.getId());
+			will(returnValue(update));
+		}});
+	}
+
+	private void expectStartTaskToAddContact(AtomicReference<ApiCall> task) {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(task, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+	}
+
+	private void expectAddContactToMailbox(
+			AtomicReference<MailboxContact> added) throws Exception {
+		context.checking(new DbExpectations() {{
+			oneOf(mailboxApi).addContact(with(mailboxProperties),
+					with(any(MailboxContact.class)));
+			will(new CaptureArgumentAction<>(added, MailboxContact.class, 1));
+		}});
+	}
+
+	private void expectStartTaskToRemoveContact(AtomicReference<ApiCall> task) {
+		context.checking(new DbExpectations() {{
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(task, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+	}
+
+	private void expectRemoveContactFromMailbox(Contact c) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(mailboxApi).deleteContact(mailboxProperties, c.getId());
+		}});
+	}
+
+	private void expectRunTaskOnIoExecutor() {
+		context.checking(new Expectations() {{
+			oneOf(ioExecutor).execute(with(any(Runnable.class)));
+			will(new RunAction());
+		}});
+	}
+
+	private void assertMailboxContactEquals(MailboxContact expected,
+			MailboxContact actual) {
+		assertEquals(expected.contactId, actual.contactId);
+		assertEquals(expected.token, actual.token);
+		assertEquals(expected.inboxId, actual.inboxId);
+		assertEquals(expected.outboxId, actual.outboxId);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxDownloadWorkerTest.java

@@ -0,0 +1,236 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.mailbox.MailboxFileId;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.mailbox.MailboxDownloadWorker.FolderFile;
+import static org.briarproject.bramble.mailbox.OwnMailboxDownloadWorker.MAX_ROUND_ROBIN_FILES;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class OwnMailboxDownloadWorkerTest
+		extends MailboxDownloadWorkerTest<OwnMailboxDownloadWorker> {
+
+	private final MailboxFolderId folderId1 =
+			new MailboxFolderId(getRandomId());
+	private final MailboxFolderId folderId2 =
+			new MailboxFolderId(getRandomId());
+	private final List<MailboxFolderId> folderIds =
+			asList(folderId1, folderId2);
+
+	public OwnMailboxDownloadWorkerTest() {
+		mailboxProperties = getMailboxProperties(true, CLIENT_SUPPORTS);
+		worker = new OwnMailboxDownloadWorker(connectivityChecker,
+				torReachabilityMonitor, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, mailboxProperties);
+	}
+
+	@Override
+	public void setUp() {
+		super.setUp();
+	}
+
+	@Test
+	public void testChecksConnectivityWhenStartedAndRemovesObserverWhenDestroyed() {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+
+	@Test
+	public void testChecksForFilesWhenConnectivityCheckSucceeds()
+			throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the connectivity check succeeds, a list-folders task should be
+		// started for the first download cycle
+		AtomicReference<ApiCall> listFoldersTask = new AtomicReference<>();
+		expectStartTask(listFoldersTask);
+		worker.onConnectivityCheckSucceeded();
+
+		// When the list-folders tasks runs and finds no folders with files
+		// to download, it should add a Tor reachability observer
+		expectCheckForFoldersWithAvailableFiles(emptyList());
+		expectAddReachabilityObserver();
+		assertFalse(listFoldersTask.get().callApi());
+
+		// When the reachability observer is called, a list-folders task should
+		// be started for the second download cycle
+		expectStartTask(listFoldersTask);
+		worker.onTorReachable();
+
+		// When the list-folders tasks runs and finds no folders with files
+		// to download, it should finish the second download cycle
+		expectCheckForFoldersWithAvailableFiles(emptyList());
+		assertFalse(listFoldersTask.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+
+	@Test
+	public void testDownloadsFilesWhenConnectivityCheckSucceeds()
+			throws Exception {
+		// When the worker is started it should start a connectivity check
+		expectStartConnectivityCheck();
+		worker.start();
+
+		// When the connectivity check succeeds, a list-folders task should be
+		// started for the first download cycle
+		AtomicReference<ApiCall> listFoldersTask = new AtomicReference<>();
+		expectStartTask(listFoldersTask);
+		worker.onConnectivityCheckSucceeded();
+
+		// When the list-folders tasks runs and finds some folders with files
+		// to download, it should start a list-files task for the first folder
+		AtomicReference<ApiCall> listFilesTask = new AtomicReference<>();
+		expectCheckForFoldersWithAvailableFiles(folderIds);
+		expectStartTask(listFilesTask);
+		assertFalse(listFoldersTask.get().callApi());
+
+		// When the first list-files task runs and finds no files to download,
+		// it should start a second list-files task for the next folder
+		expectCheckForFiles(folderId1, emptyList());
+		expectStartTask(listFilesTask);
+		assertFalse(listFilesTask.get().callApi());
+
+		// When the second list-files task runs and finds some files to
+		// download, it should create the round-robin queue and start a
+		// download task for the first file
+		AtomicReference<ApiCall> downloadTask = new AtomicReference<>();
+		expectCheckForFiles(folderId2, files);
+		expectStartTask(downloadTask);
+		assertFalse(listFilesTask.get().callApi());
+
+		// When the first download task runs it should download the file to the
+		// location provided by the file manager and start a delete task
+		AtomicReference<ApiCall> deleteTask = new AtomicReference<>();
+		expectDownloadFile(folderId2, file1);
+		expectStartTask(deleteTask);
+		assertFalse(downloadTask.get().callApi());
+
+		// When the first delete task runs it should delete the file, ignore
+		// the tolerable failure, and start a download task for the next file
+		expectDeleteFile(folderId2, file1, true); // Delete fails tolerably
+		expectStartTask(downloadTask);
+		assertFalse(deleteTask.get().callApi());
+
+		// When the second download task runs it should download the file to
+		// the location provided by the file manager and start a delete task
+		expectDownloadFile(folderId2, file2);
+		expectStartTask(deleteTask);
+		assertFalse(downloadTask.get().callApi());
+
+		// When the second delete task runs it should delete the file and
+		// start a list-inbox task to check for files that may have arrived
+		// since the first download cycle started
+		expectDeleteFile(folderId2, file2, false); // Delete succeeds
+		expectStartTask(listFoldersTask);
+		assertFalse(deleteTask.get().callApi());
+
+		// When the list-inbox tasks runs and finds no more files to download,
+		// it should add a Tor reachability observer
+		expectCheckForFoldersWithAvailableFiles(emptyList());
+		expectAddReachabilityObserver();
+		assertFalse(listFoldersTask.get().callApi());
+
+		// When the reachability observer is called, a list-inbox task should
+		// be started for the second download cycle
+		expectStartTask(listFoldersTask);
+		worker.onTorReachable();
+
+		// When the list-inbox tasks runs and finds no more files to download,
+		// it should finish the second download cycle
+		expectCheckForFoldersWithAvailableFiles(emptyList());
+		assertFalse(listFoldersTask.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// and reachability observers
+		expectRemoveObservers();
+		worker.destroy();
+	}
+
+	@Test
+	public void testRoundRobinQueueVisitsAllFolders() {
+		// Ten folders with two files each
+		Map<MailboxFolderId, Queue<MailboxFile>> available =
+				createAvailableFiles(10, 2);
+		Queue<FolderFile> queue = worker.createRoundRobinQueue(available);
+		// Check that all files were queued
+		for (MailboxFolderId folderId : available.keySet()) {
+			assertEquals(2, countFilesWithFolderId(queue, folderId));
+		}
+	}
+
+	@Test
+	public void testSizeOfRoundRobinQueueIsLimited() {
+		// Two folders with MAX_ROUND_ROBIN_FILES each
+		Map<MailboxFolderId, Queue<MailboxFile>> available =
+				createAvailableFiles(2, MAX_ROUND_ROBIN_FILES);
+		Queue<FolderFile> queue = worker.createRoundRobinQueue(available);
+		// Check that half the files in each folder were queued
+		for (MailboxFolderId folderId : available.keySet()) {
+			assertEquals(MAX_ROUND_ROBIN_FILES / 2,
+					countFilesWithFolderId(queue, folderId));
+		}
+	}
+
+	private Map<MailboxFolderId, Queue<MailboxFile>> createAvailableFiles(
+			int numFolders, int numFiles) {
+		Map<MailboxFolderId, Queue<MailboxFile>> available = new HashMap<>();
+		List<MailboxFolderId> folderIds = createFolderIds(numFolders);
+		for (MailboxFolderId folderId : folderIds) {
+			available.put(folderId, createFiles(numFiles));
+		}
+		return available;
+	}
+
+	private List<MailboxFolderId> createFolderIds(int size) {
+		List<MailboxFolderId> folderIds = new ArrayList<>(size);
+		for (int i = 0; i < size; i++) {
+			folderIds.add(new MailboxFolderId(getRandomId()));
+		}
+		return folderIds;
+	}
+
+	private Queue<MailboxFile> createFiles(int size) {
+		Queue<MailboxFile> files = new LinkedList<>();
+		for (int i = 0; i < size; i++) {
+			files.add(new MailboxFile(new MailboxFileId(getRandomId()), i));
+		}
+		return files;
+	}
+
+	private int countFilesWithFolderId(Queue<FolderFile> queue,
+			MailboxFolderId folderId) {
+		int count = 0;
+		for (FolderFile file : queue) {
+			if (file.folderId.equals(folderId)) count++;
+		}
+		return count;
+	}
+}