diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt
index d12a7a833..f74e3a5b3 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt
@@ -24,6 +24,8 @@ import org.briarproject.bramble.plugin.tor.CircumventionProvider
 import org.briarproject.bramble.plugin.tor.LinuxTorPluginFactory
 import org.briarproject.bramble.system.JavaSystemModule
 import org.briarproject.bramble.util.StringUtils.fromHexString
+import org.briarproject.briar.headless.event.WebSocketController
+import org.briarproject.briar.headless.event.WebSocketControllerImpl
 import org.briarproject.briar.headless.messaging.MessagingModule
 import java.io.File
 import java.security.GeneralSecurityException
@@ -108,7 +110,8 @@ internal class HeadlessModule(private val appDir: File) {
     @Provides
     @Singleton
     internal fun provideWebSocketHandler(
-        webSocketController: WebSocketControllerImpl): WebSocketController {
+        webSocketController: WebSocketControllerImpl
+    ): WebSocketController {
         return webSocketController
     }
 
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt
index 512d37759..881ee89cd 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt
@@ -8,6 +8,7 @@ import io.javalin.core.util.ContextUtil
 import io.javalin.core.util.Header
 import org.briarproject.briar.headless.blogs.BlogController
 import org.briarproject.briar.headless.contact.ContactController
+import org.briarproject.briar.headless.event.WebSocketController
 import org.briarproject.briar.headless.forums.ForumController
 import org.briarproject.briar.headless.messaging.MessagingController
 import java.lang.Runtime.getRuntime
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/event/OutputEvent.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/event/OutputEvent.kt
new file mode 100644
index 000000000..dc68c5c93
--- /dev/null
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/event/OutputEvent.kt
@@ -0,0 +1,13 @@
+package org.briarproject.briar.headless.event
+
+import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent
+import org.briarproject.briar.headless.messaging.output
+import javax.annotation.concurrent.Immutable
+
+@Immutable
+internal class OutputEvent(val name: String, val data: Any) {
+    val type = "event"
+}
+
+internal fun PrivateMessageReceivedEvent<*>.output(body: String) =
+    messageHeader.output(contactId, body)
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketController.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketController.kt
similarity index 77%
rename from briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketController.kt
rename to briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketController.kt
index a4abbe86c..e7f8c9fd0 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketController.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketController.kt
@@ -1,4 +1,4 @@
-package org.briarproject.briar.headless
+package org.briarproject.briar.headless.event
 
 import io.javalin.websocket.WsSession
 
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketControllerImpl.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketControllerImpl.kt
similarity index 56%
rename from briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketControllerImpl.kt
rename to briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketControllerImpl.kt
index 6e75d3bef..ad86c7e89 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/WebSocketControllerImpl.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/event/WebSocketControllerImpl.kt
@@ -1,6 +1,6 @@
-package org.briarproject.briar.headless
+package org.briarproject.briar.headless.event
 
-import io.javalin.json.JavalinJson
+import io.javalin.json.JavalinJson.toJson
 import io.javalin.websocket.WsSession
 import java.util.concurrent.ConcurrentHashMap
 import javax.annotation.concurrent.Immutable
@@ -9,21 +9,16 @@ import javax.inject.Singleton
 
 @Immutable
 @Singleton
-internal class WebSocketControllerImpl @Inject constructor() : WebSocketController {
+internal class WebSocketControllerImpl @Inject constructor() :
+    WebSocketController {
 
     override val sessions: MutableSet<WsSession> = ConcurrentHashMap.newKeySet<WsSession>()
 
     override fun sendEvent(name: String, obj: Any) {
         sessions.forEach { session ->
             val event = OutputEvent(name, obj)
-            val json = JavalinJson.toJsonMapper.map(event)
-            session.send(json)
+            session.send(toJson(event))
         }
     }
 
 }
-
-@Immutable
-internal class OutputEvent(val name: String, val data: Any) {
-    val type = "event"
-}
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
index 730294e31..c1e023e9b 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
@@ -14,7 +14,8 @@ import org.briarproject.bramble.api.system.Clock
 import org.briarproject.briar.api.messaging.*
 import org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_BODY_LENGTH
 import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent
-import org.briarproject.briar.headless.WebSocketController
+import org.briarproject.briar.headless.event.WebSocketController
+import org.briarproject.briar.headless.event.output
 import java.util.concurrent.Executor
 import javax.annotation.concurrent.Immutable
 import javax.inject.Inject
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputPrivateMessage.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputPrivateMessage.kt
index 49455e9ae..ef8897eeb 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputPrivateMessage.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputPrivateMessage.kt
@@ -3,7 +3,6 @@ package org.briarproject.briar.headless.messaging
 import org.briarproject.bramble.api.contact.ContactId
 import org.briarproject.briar.api.messaging.PrivateMessage
 import org.briarproject.briar.api.messaging.PrivateMessageHeader
-import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent
 import javax.annotation.concurrent.Immutable
 
 @Immutable
@@ -57,6 +56,3 @@ internal fun PrivateMessageHeader.output(
 
 internal fun PrivateMessage.output(contactId: ContactId, body: String) =
     OutputPrivateMessageHeader(this, contactId, body)
-
-internal fun PrivateMessageReceivedEvent<*>.output(body: String) =
-    messageHeader.output(contactId, body)
diff --git a/briar-headless/src/test/java/org/briarproject/briar/headless/event/WebSocketControllerTest.kt b/briar-headless/src/test/java/org/briarproject/briar/headless/event/WebSocketControllerTest.kt
new file mode 100644
index 000000000..a3ab33ed9
--- /dev/null
+++ b/briar-headless/src/test/java/org/briarproject/briar/headless/event/WebSocketControllerTest.kt
@@ -0,0 +1,47 @@
+package org.briarproject.briar.headless.event
+
+import io.javalin.json.JavalinJson.toJson
+import io.javalin.websocket.WsSession
+import io.mockk.*
+import org.briarproject.briar.api.messaging.PrivateMessageHeader
+import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent
+import org.briarproject.briar.headless.ControllerTest
+import org.briarproject.briar.headless.messaging.EVENT_PRIVATE_MESSAGE
+import org.briarproject.briar.headless.messaging.output
+import org.junit.jupiter.api.Test
+
+internal class WebSocketControllerTest : ControllerTest() {
+
+    private val session = mockk<WsSession>()
+    private val controller = WebSocketControllerImpl()
+
+    private val header =
+        PrivateMessageHeader(message.id, group.id, timestamp, true, true, true, true)
+    private val event = PrivateMessageReceivedEvent(header, contact.id)
+    private val outputEvent = OutputEvent(EVENT_PRIVATE_MESSAGE, event.output(body))
+
+    @Test
+    fun testSessionSend() {
+        val slot = CapturingSlot<String>()
+
+        every { session.send(capture(slot)) } just Runs
+
+        controller.sessions.add(session)
+        controller.sendEvent(EVENT_PRIVATE_MESSAGE, event.output(body))
+
+        assertJsonEquals(slot.captured, outputEvent)
+    }
+
+    @Test
+    fun testOutputPrivateMessageReceivedEvent() {
+        val json = """
+        {
+            "type": "event",
+            "name": "org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent",
+            "data": ${toJson(header.output(contact.id, body))}
+        }
+        """
+        assertJsonEquals(json, outputEvent)
+    }
+
+}
diff --git a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
index a15bc782c..891baaa7b 100644
--- a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
+++ b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
@@ -13,7 +13,8 @@ import org.briarproject.briar.api.messaging.*
 import org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_BODY_LENGTH
 import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent
 import org.briarproject.briar.headless.ControllerTest
-import org.briarproject.briar.headless.WebSocketController
+import org.briarproject.briar.headless.event.WebSocketController
+import org.briarproject.briar.headless.event.output
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertThrows
 import org.junit.jupiter.api.Test