Pass a connection handler to plugins when polling.

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
@@ -17,13 +16,11 @@ 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.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
 import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
-import org.briarproject.bramble.api.plugin.simplex.SimplexPluginCallback;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
@@ -95,7 +92,7 @@ class PluginManagerImpl implements PluginManager, Service {
 		LOG.info("Starting simplex plugins");
 		for (SimplexPluginFactory f : pluginConfig.getSimplexFactories()) {
 			TransportId t = f.getId();
-			SimplexPlugin s = f.createPlugin(new SimplexCallback(t));
+			SimplexPlugin s = f.createPlugin(new Callback(t));
 			if (s == null) {
 				if (LOG.isLoggable(WARNING))
 					LOG.warning("Could not create plugin for " + t);
@@ -111,7 +108,7 @@ class PluginManagerImpl implements PluginManager, Service {
 		LOG.info("Starting duplex plugins");
 		for (DuplexPluginFactory f : pluginConfig.getDuplexFactories()) {
 			TransportId t = f.getId();
-			DuplexPlugin d = f.createPlugin(new DuplexCallback(t));
+			DuplexPlugin d = f.createPlugin(new Callback(t));
 			if (d == null) {
 				if (LOG.isLoggable(WARNING))
 					LOG.warning("Could not create plugin for " + t);
@@ -242,12 +239,11 @@ class PluginManagerImpl implements PluginManager, Service {
 		}
 	}
 
-	@NotNullByDefault
-	private abstract class PluginCallbackImpl implements PluginCallback {
+	private class Callback implements PluginCallback {
 
-		protected final TransportId id;
+		private final TransportId id;
 
-		PluginCallbackImpl(TransportId id) {
+		private Callback(TransportId id) {
 			this.id = id;
 		}
 
@@ -298,44 +294,21 @@ class PluginManagerImpl implements PluginManager, Service {
 		public void transportDisabled() {
 			eventBus.broadcast(new TransportDisabledEvent(id));
 		}
-	}
-
-	@NotNullByDefault
-	private class SimplexCallback extends PluginCallbackImpl
-			implements SimplexPluginCallback {
-
-		private SimplexCallback(TransportId id) {
-			super(id);
-		}
 
 		@Override
-		public void readerCreated(TransportConnectionReader r) {
-			connectionManager.manageIncomingConnection(id, r);
-		}
-
-		@Override
-		public void writerCreated(ContactId c, TransportConnectionWriter w) {
-			connectionManager.manageOutgoingConnection(c, id, w);
-		}
-	}
-
-	@NotNullByDefault
-	private class DuplexCallback extends PluginCallbackImpl
-			implements DuplexPluginCallback {
-
-		private DuplexCallback(TransportId id) {
-			super(id);
-		}
-
-		@Override
-		public void incomingConnectionCreated(DuplexTransportConnection d) {
+		public void handleConnection(DuplexTransportConnection d) {
 			connectionManager.manageIncomingConnection(id, d);
 		}
 
 		@Override
-		public void outgoingConnectionCreated(ContactId c,
-				DuplexTransportConnection d) {
-			connectionManager.manageOutgoingConnection(c, id, d);
+		public void handleReader(TransportConnectionReader r) {
+			connectionManager.manageIncomingConnection(id, r);
+		}
+
+		@Override
+		public void handleWriter(TransportConnectionWriter w) {
+			// TODO: Support simplex plugins that write to incoming connections
+			throw new UnsupportedOperationException();
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/PollerImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.plugin;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
 import org.briarproject.bramble.api.db.DbException;
@@ -7,10 +8,12 @@ import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
 import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.api.plugin.ConnectionRegistry;
 import org.briarproject.bramble.api.plugin.Plugin;
 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.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -26,9 +29,11 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.Scheduler;
 
 import java.security.SecureRandom;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
@@ -211,9 +216,14 @@ class PollerImpl implements Poller, EventListener {
 					transportPropertyManager.getRemoteProperties(t);
 			Collection<ContactId> connected =
 					connectionRegistry.getConnectedContacts(t);
-			remote = new HashMap<>(remote);
-			remote.keySet().removeAll(connected);
-			if (!remote.isEmpty()) p.poll(remote);
+			Collection<Pair<TransportProperties, ConnectionHandler>>
+					properties = new ArrayList<>();
+			for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
+				ContactId c = e.getKey();
+				if (!connected.contains(c))
+					properties.add(new Pair<>(e.getValue(), new Handler(c, t)));
+			}
+			if (!properties.isEmpty()) p.poll(properties);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 		}
@@ -261,4 +271,33 @@ class PollerImpl implements Poller, EventListener {
 			poll(plugin);
 		}
 	}
+
+	private class Handler implements ConnectionHandler {
+
+		private final ContactId contactId;
+		private final TransportId transportId;
+
+		private Handler(ContactId contactId, TransportId transportId) {
+			this.contactId = contactId;
+			this.transportId = transportId;
+		}
+
+		@Override
+		public void handleConnection(DuplexTransportConnection c) {
+			connectionManager.manageOutgoingConnection(contactId,
+					transportId, c);
+		}
+
+		@Override
+		public void handleReader(TransportConnectionReader r) {
+			// TODO: Support simplex plugins that read from outgoing connections
+			throw new UnsupportedOperationException();
+		}
+
+		@Override
+		public void handleWriter(TransportConnectionWriter w) {
+			connectionManager.manageOutgoingConnection(contactId,
+					transportId, w);
+		}
+	}
 }

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

@@ -1,7 +1,7 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
 import org.briarproject.bramble.api.FormatException;
-import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
@@ -12,10 +12,11 @@ import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListen
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
 import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
@@ -26,8 +27,7 @@ import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 
 import java.io.IOException;
 import java.security.SecureRandom;
-import java.util.Map;
-import java.util.Map.Entry;
+import java.util.Collection;
 import java.util.UUID;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -37,6 +37,7 @@ import javax.annotation.Nullable;
 
 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.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_BT_ENABLE;
@@ -54,14 +55,14 @@ import static org.briarproject.bramble.util.StringUtils.macToString;
 abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	private static final Logger LOG =
-			Logger.getLogger(BluetoothPlugin.class.getName());
+			getLogger(BluetoothPlugin.class.getName());
 
 	final BluetoothConnectionLimiter connectionLimiter;
 
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
 	private final Backoff backoff;
-	private final DuplexPluginCallback callback;
+	private final PluginCallback callback;
 	private final int maxLatency;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
@@ -103,7 +104,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			Executor ioExecutor, SecureRandom secureRandom,
-			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
+			Backoff backoff, PluginCallback callback, int maxLatency) {
 		this.connectionLimiter = connectionLimiter;
 		this.ioExecutor = ioExecutor;
 		this.secureRandom = secureRandom;
@@ -226,7 +227,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			}
 			backoff.reset();
 			if (connectionLimiter.contactConnectionOpened(conn))
-				callback.incomingConnectionCreated(conn);
+				callback.handleConnection(conn);
 			if (!running) return;
 		}
 	}
@@ -255,29 +256,32 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	}
 
 	@Override
-	public void poll(Map<ContactId, TransportProperties> contacts) {
+	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+			properties) {
 		if (!isRunning() || !shouldAllowContactConnections()) return;
 		backoff.increment();
-		// Try to connect to known devices in parallel
-		for (Entry<ContactId, TransportProperties> e : contacts.entrySet()) {
-			String address = e.getValue().get(PROP_ADDRESS);
-			if (isNullOrEmpty(address)) continue;
-			String uuid = e.getValue().get(PROP_UUID);
-			if (isNullOrEmpty(uuid)) continue;
-			ContactId c = e.getKey();
-			ioExecutor.execute(() -> {
-				if (!isRunning() || !shouldAllowContactConnections()) return;
-				if (!connectionLimiter.canOpenContactConnection()) return;
-				DuplexTransportConnection conn = connect(address, uuid);
-				if (conn != null) {
-					backoff.reset();
-					if (connectionLimiter.contactConnectionOpened(conn))
-						callback.outgoingConnectionCreated(c, conn);
-				}
-			});
+		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
+			connect(p.getFirst(), p.getSecond());
 		}
 	}
 
+	private void connect(TransportProperties p, ConnectionHandler h) {
+		String address = p.get(PROP_ADDRESS);
+		if (isNullOrEmpty(address)) return;
+		String uuid = p.get(PROP_UUID);
+		if (isNullOrEmpty(uuid)) return;
+		ioExecutor.execute(() -> {
+			if (!isRunning() || !shouldAllowContactConnections()) return;
+			if (!connectionLimiter.canOpenContactConnection()) return;
+			DuplexTransportConnection d = createConnection(p);
+			if (d != null) {
+				backoff.reset();
+				if (connectionLimiter.contactConnectionOpened(d))
+					h.handleConnection(d);
+			}
+		});
+	}
+
 	@Nullable
 	private DuplexTransportConnection connect(String address, String uuid) {
 		// Validate the address

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

@@ -1,10 +1,10 @@
 package org.briarproject.bramble.plugin.file;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
-import org.briarproject.bramble.api.plugin.simplex.SimplexPluginCallback;
 import org.briarproject.bramble.api.properties.TransportProperties;
 
 import java.io.File;
@@ -14,6 +14,7 @@ import java.io.IOException;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.FileConstants.PROP_PATH;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -22,9 +23,9 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 abstract class FilePlugin implements SimplexPlugin {
 
 	private static final Logger LOG =
-			Logger.getLogger(FilePlugin.class.getName());
+			getLogger(FilePlugin.class.getName());
 
-	protected final SimplexPluginCallback callback;
+	protected final PluginCallback callback;
 	protected final int maxLatency;
 
 	protected abstract void writerFinished(File f, boolean exception);
@@ -32,7 +33,7 @@ abstract class FilePlugin implements SimplexPlugin {
 	protected abstract void readerFinished(File f, boolean exception,
 			boolean recognised);
 
-	FilePlugin(SimplexPluginCallback callback, int maxLatency) {
+	FilePlugin(PluginCallback callback, int maxLatency) {
 		this.callback = callback;
 		this.maxLatency = maxLatency;
 	}

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

@@ -6,13 +6,12 @@ import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.util.IoUtils;
-import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.net.Inet4Address;
@@ -29,20 +28,24 @@ import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import static java.util.Collections.addAll;
+import static java.util.Collections.sort;
 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.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PREF_LAN_IP_PORTS;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PROP_IP_PORTS;
 import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+import static org.briarproject.bramble.util.StringUtils.join;
 
 @NotNullByDefault
 class LanTcpPlugin extends TcpPlugin {
 
-	private static final Logger LOG =
-			Logger.getLogger(LanTcpPlugin.class.getName());
+	private static final Logger LOG = getLogger(LanTcpPlugin.class.getName());
 
 	private static final LanAddressComparator ADDRESS_COMPARATOR =
 			new LanAddressComparator();
@@ -50,8 +53,8 @@ class LanTcpPlugin extends TcpPlugin {
 	private static final int MAX_ADDRESSES = 4;
 	private static final String SEPARATOR = ",";
 
-	LanTcpPlugin(Executor ioExecutor, Backoff backoff,
-			DuplexPluginCallback callback, int maxLatency, int maxIdleTime) {
+	LanTcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
+			int maxLatency, int maxIdleTime) {
 		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime);
 	}
 
@@ -77,12 +80,12 @@ class LanTcpPlugin extends TcpPlugin {
 				locals.add(new InetSocketAddress(local, 0));
 			}
 		}
-		Collections.sort(locals, ADDRESS_COMPARATOR);
+		sort(locals, ADDRESS_COMPARATOR);
 		return locals;
 	}
 
 	private List<InetSocketAddress> parseSocketAddresses(String ipPorts) {
-		if (StringUtils.isNullOrEmpty(ipPorts)) return Collections.emptyList();
+		if (isNullOrEmpty(ipPorts)) return Collections.emptyList();
 		String[] split = ipPorts.split(SEPARATOR);
 		List<InetSocketAddress> addresses = new ArrayList<>();
 		for (String ipPort : split) {
@@ -98,24 +101,24 @@ class LanTcpPlugin extends TcpPlugin {
 		// Get the list of recently used addresses
 		String setting = callback.getSettings().get(PREF_LAN_IP_PORTS);
 		List<String> recent = new ArrayList<>();
-		if (!StringUtils.isNullOrEmpty(setting))
-			Collections.addAll(recent, setting.split(SEPARATOR));
+		if (!isNullOrEmpty(setting))
+			addAll(recent, setting.split(SEPARATOR));
 		// Is the address already in the list?
 		if (recent.remove(ipPort)) {
 			// Move the address to the start of the list
 			recent.add(0, ipPort);
-			setting = StringUtils.join(recent, SEPARATOR);
+			setting = join(recent, SEPARATOR);
 		} else {
 			// Add the address to the start of the list
 			recent.add(0, ipPort);
 			// Drop the least recently used address if the list is full
 			if (recent.size() > MAX_ADDRESSES)
 				recent = recent.subList(0, MAX_ADDRESSES);
-			setting = StringUtils.join(recent, SEPARATOR);
+			setting = join(recent, SEPARATOR);
 			// Update the list of addresses shared with contacts
 			List<String> shared = new ArrayList<>(recent);
-			Collections.sort(shared);
-			String property = StringUtils.join(shared, SEPARATOR);
+			sort(shared);
+			String property = join(shared, SEPARATOR);
 			TransportProperties properties = new TransportProperties();
 			properties.put(PROP_IP_PORTS, property);
 			callback.mergeLocalProperties(properties);

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

@@ -3,9 +3,9 @@ package org.briarproject.bramble.plugin.tcp;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.BackoffFactory;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 
 import java.util.concurrent.Executor;
@@ -44,7 +44,7 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 	}
 
 	@Override
-	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+	public DuplexPlugin createPlugin(PluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		return new LanTcpPlugin(ioExecutor, backoff, callback, MAX_LATENCY,

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

@@ -1,18 +1,18 @@
 package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.PoliteExecutor;
-import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.util.IoUtils;
-import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.net.InetAddress;
@@ -27,8 +27,6 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Enumeration;
 import java.util.List;
-import java.util.Map;
-import java.util.Map.Entry;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
@@ -41,21 +39,23 @@ import static java.util.Collections.emptyList;
 import static java.util.Collections.list;
 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.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 abstract class TcpPlugin implements DuplexPlugin {
 
+	private static final Logger LOG = getLogger(TcpPlugin.class.getName());
+
 	private static final Pattern DOTTED_QUAD =
 			Pattern.compile("^\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}$");
-	private static final Logger LOG =
-			Logger.getLogger(TcpPlugin.class.getName());
 
 	protected final Executor ioExecutor, bindExecutor;
 	protected final Backoff backoff;
-	protected final DuplexPluginCallback callback;
+	protected final PluginCallback callback;
 	protected final int maxLatency, maxIdleTime, socketTimeout;
 	protected final AtomicBoolean used = new AtomicBoolean(false);
 
@@ -86,8 +86,8 @@ abstract class TcpPlugin implements DuplexPlugin {
 	 */
 	protected abstract boolean isConnectable(InetSocketAddress remote);
 
-	TcpPlugin(Executor ioExecutor, Backoff backoff,
-			DuplexPluginCallback callback, int maxLatency, int maxIdleTime) {
+	TcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
+			int maxLatency, int maxIdleTime) {
 		this.ioExecutor = ioExecutor;
 		this.backoff = backoff;
 		this.callback = callback;
@@ -180,8 +180,7 @@ abstract class TcpPlugin implements DuplexPlugin {
 				LOG.info("Connection from " +
 						scrubSocketAddress(s.getRemoteSocketAddress()));
 			backoff.reset();
-			TcpTransportConnection conn = new TcpTransportConnection(this, s);
-			callback.incomingConnectionCreated(conn);
+			callback.handleConnection(new TcpTransportConnection(this, s));
 		}
 	}
 
@@ -207,20 +206,21 @@ abstract class TcpPlugin implements DuplexPlugin {
 	}
 
 	@Override
-	public void poll(Map<ContactId, TransportProperties> contacts) {
+	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+			properties) {
 		if (!isRunning()) return;
 		backoff.increment();
-		for (Entry<ContactId, TransportProperties> e : contacts.entrySet()) {
-			connectAndCallBack(e.getKey(), e.getValue());
+		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
+			connect(p.getFirst(), p.getSecond());
 		}
 	}
 
-	private void connectAndCallBack(ContactId c, TransportProperties p) {
+	private void connect(TransportProperties p, ConnectionHandler h) {
 		ioExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
 			if (d != null) {
 				backoff.reset();
-				callback.outgoingConnectionCreated(c, d);
+				h.handleConnection(d);
 			}
 		});
 	}
@@ -263,7 +263,7 @@ abstract class TcpPlugin implements DuplexPlugin {
 
 	@Nullable
 	InetSocketAddress parseSocketAddress(String ipPort) {
-		if (StringUtils.isNullOrEmpty(ipPort)) return null;
+		if (isNullOrEmpty(ipPort)) return null;
 		String[] split = ipPort.split(":");
 		if (split.length != 2) return null;
 		String addr = split[0], port = split[1];

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

@@ -3,18 +3,19 @@ package org.briarproject.bramble.plugin.tcp;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.properties.TransportProperties;
 
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
-import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.Executor;
 
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.plugin.WanTcpConstants.ID;
 
 @MethodsNotNullByDefault
@@ -28,7 +29,7 @@ class WanTcpPlugin extends TcpPlugin {
 	private volatile MappingResult mappingResult;
 
 	WanTcpPlugin(Executor ioExecutor, Backoff backoff, PortMapper portMapper,
-			DuplexPluginCallback callback, int maxLatency, int maxIdleTime) {
+			PluginCallback callback, int maxLatency, int maxIdleTime) {
 		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime);
 		this.portMapper = portMapper;
 	}
@@ -80,8 +81,8 @@ class WanTcpPlugin extends TcpPlugin {
 	protected List<InetSocketAddress> getRemoteSocketAddresses(
 			TransportProperties p) {
 		InetSocketAddress parsed = parseSocketAddress(p.get(PROP_IP_PORT));
-		if (parsed == null) return Collections.emptyList();
-		return Collections.singletonList(parsed);
+		if (parsed == null) return emptyList();
+		return singletonList(parsed);
 	}
 
 	@Override

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

@@ -4,9 +4,9 @@ import org.briarproject.bramble.api.lifecycle.ShutdownManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.BackoffFactory;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 
 import java.util.concurrent.Executor;
@@ -47,7 +47,7 @@ public class WanTcpPluginFactory implements DuplexPluginFactory {
 	}
 
 	@Override
-	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+	public DuplexPlugin createPlugin(PluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		return new WanTcpPlugin(ioExecutor, backoff,

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

@@ -4,9 +4,9 @@ import net.freehaven.tor.control.EventHandler;
 import net.freehaven.tor.control.TorControlConnection;
 
 import org.briarproject.bramble.PoliteExecutor;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.battery.event.BatteryEvent;
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
@@ -17,11 +17,12 @@ import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
@@ -47,7 +48,6 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Scanner;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -60,6 +60,7 @@ import javax.net.SocketFactory;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static net.freehaven.tor.control.TorControlCommands.HS_ADDRESS;
 import static net.freehaven.tor.control.TorControlCommands.HS_PRIVKEY;
 import static org.briarproject.bramble.api.plugin.TorConstants.CONTROL_PORT;
@@ -81,8 +82,7 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 @ParametersNotNullByDefault
 abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
-	private static final Logger LOG =
-			Logger.getLogger(TorPlugin.class.getName());
+	private static final Logger LOG = getLogger(TorPlugin.class.getName());
 
 	private static final String[] EVENTS = {
 			"CIRC", "ORCONN", "HS_DESC", "NOTICE", "WARN", "ERR"
@@ -100,7 +100,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private final Clock clock;
 	private final BatteryManager batteryManager;
 	private final Backoff backoff;
-	private final DuplexPluginCallback callback;
+	private final PluginCallback callback;
 	private final String architecture;
 	private final CircumventionProvider circumventionProvider;
 	private final ResourceProvider resourceProvider;
@@ -126,7 +126,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			Clock clock, ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager, Backoff backoff,
-			DuplexPluginCallback callback, String architecture, int maxLatency,
+			PluginCallback callback, String architecture, int maxLatency,
 			int maxIdleTime, File torDirectory) {
 		this.ioExecutor = ioExecutor;
 		this.networkManager = networkManager;
@@ -458,8 +458,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 			LOG.info("Connection received");
 			backoff.reset();
-			TorTransportConnection conn = new TorTransportConnection(this, s);
-			callback.incomingConnectionCreated(conn);
+			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
 
@@ -521,20 +520,21 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	@Override
-	public void poll(Map<ContactId, TransportProperties> contacts) {
+	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+			properties) {
 		if (!isRunning()) return;
 		backoff.increment();
-		for (Entry<ContactId, TransportProperties> e : contacts.entrySet()) {
-			connectAndCallBack(e.getKey(), e.getValue());
+		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
+			connect(p.getFirst(), p.getSecond());
 		}
 	}
 
-	private void connectAndCallBack(ContactId c, TransportProperties p) {
+	private void connect(TransportProperties p, ConnectionHandler h) {
 		ioExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
 			if (d != null) {
 				backoff.reset();
-				callback.outgoingConnectionCreated(c, d);
+				h.handleConnection(d);
 			}
 		});
 	}

bramble-core/src/test/java/org/briarproject/bramble/plugin/PluginManagerImplTest.java

@@ -2,14 +2,13 @@ package org.briarproject.bramble.plugin;
 
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.plugin.ConnectionManager;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
-import org.briarproject.bramble.api.plugin.simplex.SimplexPluginCallback;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.settings.SettingsManager;
@@ -78,15 +77,14 @@ public class PluginManagerImplTest extends BrambleTestCase {
 					simplexFailFactory)));
 			oneOf(simplexFactory).getId();
 			will(returnValue(simplexId));
-			oneOf(simplexFactory).createPlugin(with(any(
-					SimplexPluginCallback.class)));
+			oneOf(simplexFactory).createPlugin(with(any(PluginCallback.class)));
 			will(returnValue(simplexPlugin)); // Created
 			oneOf(simplexPlugin).start();
 			// Second simplex plugin
 			oneOf(simplexFailFactory).getId();
 			will(returnValue(simplexFailId));
 			oneOf(simplexFailFactory).createPlugin(with(any(
-					SimplexPluginCallback.class)));
+					PluginCallback.class)));
 			will(returnValue(simplexFailPlugin)); // Created
 			oneOf(simplexFailPlugin).start();
 			will(throwException(new PluginException()));
@@ -95,15 +93,14 @@ public class PluginManagerImplTest extends BrambleTestCase {
 			will(returnValue(Arrays.asList(duplexFactory, duplexFailFactory)));
 			oneOf(duplexFactory).getId();
 			will(returnValue(duplexId));
-			oneOf(duplexFactory).createPlugin(with(any(
-					DuplexPluginCallback.class)));
+			oneOf(duplexFactory).createPlugin(with(any(PluginCallback.class)));
 			will(returnValue(duplexPlugin)); // Created
 			oneOf(duplexPlugin).start();
 			// Second duplex plugin
 			oneOf(duplexFailFactory).getId();
 			will(returnValue(duplexFailId));
 			oneOf(duplexFailFactory).createPlugin(with(any(
-					DuplexPluginCallback.class)));
+					PluginCallback.class)));
 			will(returnValue(null)); // Failed to create a plugin
 			// stop()
 			// Stop the plugins

bramble-core/src/test/java/org/briarproject/bramble/plugin/PollerImplTest.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.plugin;
 
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
 import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.api.plugin.ConnectionRegistry;
 import org.briarproject.bramble.api.plugin.Plugin;
@@ -37,6 +38,8 @@ import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.test.CollectionMatcher.collectionOf;
+import static org.briarproject.bramble.test.PairMatcher.pairOf;
 import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
 
@@ -354,7 +357,8 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(connectionRegistry).getConnectedContacts(transportId);
 			will(returnValue(emptyList()));
 			// Poll the plugin
-			oneOf(plugin).poll(singletonMap(contactId, properties));
+			oneOf(plugin).poll(with(collectionOf(
+					pairOf(equal(properties), any(ConnectionHandler.class)))));
 		}});
 
 		poller.eventOccurred(new TransportEnabledEvent(transportId));

bramble-core/src/test/java/org/briarproject/bramble/plugin/tcp/LanTcpPluginTest.java

@@ -1,12 +1,13 @@
 package org.briarproject.bramble.plugin.tcp;
 
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.PluginCallback;
+import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
@@ -21,13 +22,14 @@ import java.net.InetSocketAddress;
 import java.net.NetworkInterface;
 import java.net.ServerSocket;
 import java.net.Socket;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.Executor;
-import java.util.concurrent.Executors;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import static java.net.NetworkInterface.getNetworkInterfaces;
+import static java.util.Collections.list;
+import static java.util.concurrent.Executors.newCachedThreadPool;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
@@ -39,10 +41,13 @@ import static org.junit.Assert.assertTrue;
 public class LanTcpPluginTest extends BrambleTestCase {
 
 	private final Backoff backoff = new TestBackoff();
+	private final ExecutorService ioExecutor = newCachedThreadPool();
 
 	@Test
 	public void testAddressesAreOnSameLan() {
-		LanTcpPlugin plugin = new LanTcpPlugin(null, null, null, 0, 0);
+		Callback callback = new Callback();
+		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, backoff, callback,
+				0, 0);
 		// Local and remote in 10.0.0.0/8 should return true
 		assertTrue(plugin.addressesAreOnSameLan(makeAddress(10, 0, 0, 0),
 				makeAddress(10, 255, 255, 255)));
@@ -93,8 +98,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			return;
 		}
 		Callback callback = new Callback();
-		Executor executor = Executors.newCachedThreadPool();
-		DuplexPlugin plugin = new LanTcpPlugin(executor, backoff, callback,
+		DuplexPlugin plugin = new LanTcpPlugin(ioExecutor, backoff, callback,
 				0, 0);
 		plugin.start();
 		// The plugin should have bound a socket and stored the port number
@@ -129,8 +133,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			return;
 		}
 		Callback callback = new Callback();
-		Executor executor = Executors.newCachedThreadPool();
-		DuplexPlugin plugin = new LanTcpPlugin(executor, backoff, callback,
+		DuplexPlugin plugin = new LanTcpPlugin(ioExecutor, backoff, callback,
 				0, 0);
 		plugin.start();
 		// The plugin should have bound a socket and stored the port number
@@ -179,8 +182,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			return;
 		}
 		Callback callback = new Callback();
-		Executor executor = Executors.newCachedThreadPool();
-		DuplexPlugin plugin = new LanTcpPlugin(executor, backoff, callback,
+		DuplexPlugin plugin = new LanTcpPlugin(ioExecutor, backoff, callback,
 				0, 0);
 		plugin.start();
 		assertTrue(callback.propertiesLatch.await(5, SECONDS));
@@ -228,8 +230,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			return;
 		}
 		Callback callback = new Callback();
-		Executor executor = Executors.newCachedThreadPool();
-		DuplexPlugin plugin = new LanTcpPlugin(executor, backoff, callback,
+		DuplexPlugin plugin = new LanTcpPlugin(ioExecutor, backoff, callback,
 				0, 0);
 		plugin.start();
 		// The plugin should have bound a socket and stored the port number
@@ -327,9 +328,8 @@ public class LanTcpPluginTest extends BrambleTestCase {
 	}
 
 	private boolean systemHasLocalIpv4Address() throws Exception {
-		for (NetworkInterface i : Collections.list(
-				NetworkInterface.getNetworkInterfaces())) {
-			for (InetAddress a : Collections.list(i.getInetAddresses())) {
+		for (NetworkInterface i : list(getNetworkInterfaces())) {
+			for (InetAddress a : list(i.getInetAddresses())) {
 				if (a instanceof Inet4Address)
 					return a.isLinkLocalAddress() || a.isSiteLocalAddress();
 			}
@@ -338,7 +338,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 	}
 
 	@NotNullByDefault
-	private static class Callback implements DuplexPluginCallback {
+	private static class Callback implements PluginCallback {
 
 		private final CountDownLatch propertiesLatch = new CountDownLatch(1);
 		private final CountDownLatch connectionsLatch = new CountDownLatch(1);
@@ -364,16 +364,6 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			propertiesLatch.countDown();
 		}
 
-		@Override
-		public void incomingConnectionCreated(DuplexTransportConnection d) {
-			connectionsLatch.countDown();
-		}
-
-		@Override
-		public void outgoingConnectionCreated(ContactId c,
-				DuplexTransportConnection d) {
-		}
-
 		@Override
 		public void transportEnabled() {
 		}
@@ -381,6 +371,19 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		@Override
 		public void transportDisabled() {
 		}
+
+		@Override
+		public void handleConnection(DuplexTransportConnection d) {
+			connectionsLatch.countDown();
+		}
+
+		@Override
+		public void handleReader(TransportConnectionReader r) {
+		}
+
+		@Override
+		public void handleWriter(TransportConnectionWriter w) {
+		}
 	}
 
 	private static class TestBackoff implements Backoff {

bramble-core/src/test/java/org/briarproject/bramble/test/CollectionMatcher.java

@@ -0,0 +1,39 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.hamcrest.BaseMatcher;
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+
+import java.util.Collection;
+
+import javax.annotation.Nullable;
+
+@NotNullByDefault
+public class CollectionMatcher<T> extends BaseMatcher<Collection<T>> {
+
+	private final Matcher<T> elementMatcher;
+
+	public CollectionMatcher(Matcher<T> elementMatcher) {
+		this.elementMatcher = elementMatcher;
+	}
+
+	@Override
+	public boolean matches(@Nullable Object item) {
+		if (!(item instanceof Collection)) return false;
+		Collection collection = (Collection) item;
+		for (Object element : collection) {
+			if (!elementMatcher.matches(element)) return false;
+		}
+		return true;
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("matches a collection");
+	}
+
+	public static <T> CollectionMatcher<T> collectionOf(Matcher<T> t) {
+		return new CollectionMatcher<>(t);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/PairMatcher.java

@@ -0,0 +1,38 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.hamcrest.BaseMatcher;
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+
+import javax.annotation.Nullable;
+
+@NotNullByDefault
+public class PairMatcher<A, B> extends BaseMatcher<Pair<A, B>> {
+
+	private final Matcher<A> firstMatcher;
+	private final Matcher<B> secondMatcher;
+
+	public PairMatcher(Matcher<A> firstMatcher, Matcher<B> secondMatcher) {
+		this.firstMatcher = firstMatcher;
+		this.secondMatcher = secondMatcher;
+	}
+
+	@Override
+	public boolean matches(@Nullable Object item) {
+		if (!(item instanceof Pair)) return false;
+		Pair pair = (Pair) item;
+		return firstMatcher.matches(pair.getFirst()) &&
+				secondMatcher.matches(pair.getSecond());
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("matches a pair");
+	}
+
+	public static <A, B> PairMatcher<A, B> pairOf(Matcher<A> a, Matcher<B> b) {
+		return new PairMatcher<>(a, b);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/TestPluginConfigModule.java

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.test;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
-import org.briarproject.bramble.api.plugin.simplex.SimplexPluginCallback;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 
 import java.util.Collection;
@@ -40,7 +40,7 @@ public class TestPluginConfigModule {
 
 		@Override
 		@Nullable
-		public SimplexPlugin createPlugin(SimplexPluginCallback callback) {
+		public SimplexPlugin createPlugin(PluginCallback callback) {
 			return null;
 		}
 	};