Expose participantIdentity on RoomEvent.DataReceived

.changeset/data-received-participant-identity.md

@@ -0,0 +1,9 @@
+---
+"client-sdk-android": patch
+---
+
+Expose `participantIdentity` on `RoomEvent.DataReceived`. The event's `participant` is nullable and is null whenever the sender is not in the room — data sent through the Server API, or by a participant that has already left. In that case the receiver had no way to tell who sent the data, because the engine dropped the identity before building the event: `onUserPacket` was handed only the inner `UserPacket`, while the authoritative identity lives on the enclosing `DataPacket`.
+
+The internal engine listener now forwards that identity, and it is reported on every `DataReceived` event whether or not the sender resolves to a `RemoteParticipant`.
+
+This matches the JavaScript SDK (livekit/client-sdk-js#2092).

livekit-android-sdk/src/main/java/io/livekit/android/events/RoomEvent.kt

@@ -247,6 +247,19 @@ sealed class RoomEvent(val room: Room) : Event() {
     /**
      * Received data published by another participant
      *
+     * [participant] is null when the sender is not in the room, such as data published through
+     * the Server API or by a participant that has already left. Use [participantIdentity] to
+     * attribute the data in that case.
+     *
+     * ```
+     * room.events.collect { event ->
+     *     if (event is RoomEvent.DataReceived) {
+     *         val sender = event.participant?.identity?.value ?: event.participantIdentity
+     *         println("$sender sent ${event.data.size} bytes")
+     *     }
+     * }
+     * ```
+     *
      * @param data the published data
      * @param participant the participant if available
      */
@@ -256,8 +269,27 @@ sealed class RoomEvent(val room: Room) : Event() {
         val participant: RemoteParticipant?,
         val topic: String?,
         val encryptionType: LivekitModels.Encryption.Type,
+        /**
+         * Identity of the sender. Reported even when [participant] is null because the
+         * sender is not (or is no longer) a participant in this room.
+         */
+        val participantIdentity: String = "",
     ) :
-        RoomEvent(room)
+        RoomEvent(room) {
+        /**
+         * Retains the pre-[participantIdentity] JVM constructor signature, so modules compiled
+         * against an earlier SDK keep linking. A Kotlin default argument alone would not: it
+         * emits the full-arity constructor plus a synthetic one, and the old five-argument
+         * signature would disappear.
+         */
+        constructor(
+            room: Room,
+            data: ByteArray,
+            participant: RemoteParticipant?,
+            topic: String?,
+            encryptionType: LivekitModels.Encryption.Type,
+        ) : this(room, data, participant, topic, encryptionType, "")
+    }
 
     /**
      * The connection quality for a participant has changed.

livekit-android-sdk/src/main/java/io/livekit/android/room/RTCEngine.kt

@@ -1186,7 +1186,7 @@ internal constructor(
         fun onRoomUpdate(update: LivekitModels.Room)
         fun onConnectionQuality(updates: List<LivekitRtc.ConnectionQualityInfo>)
         fun onSpeakersChanged(speakers: List<LivekitModels.SpeakerInfo>)
-        fun onUserPacket(packet: LivekitModels.UserPacket, kind: LivekitModels.DataPacket.Kind, encryptionType: LivekitModels.Encryption.Type)
+        fun onUserPacket(packet: LivekitModels.UserPacket, kind: LivekitModels.DataPacket.Kind, encryptionType: LivekitModels.Encryption.Type, participantIdentity: String)
         fun onStreamStateUpdate(streamStates: List<LivekitRtc.StreamStateInfo>)
         fun onSubscribedQualityUpdate(subscribedQualityUpdate: LivekitRtc.SubscribedQualityUpdate)
         fun onRequestSubscribedCodecRefresh() {}
@@ -1550,7 +1550,7 @@ internal constructor(
             }
 
             LivekitModels.DataPacket.ValueCase.USER -> {
-                listener?.onUserPacket(dp.user, dp.kind, encryptionType)
+                listener?.onUserPacket(dp.user, dp.kind, encryptionType, dp.participantIdentity)
             }
 
             LivekitModels.DataPacket.ValueCase.SIP_DTMF -> {

livekit-android-sdk/src/main/java/io/livekit/android/room/Room.kt

@@ -1391,7 +1391,7 @@ constructor(
     /**
      * @suppress
      */
-    override fun onUserPacket(packet: LivekitModels.UserPacket, kind: LivekitModels.DataPacket.Kind, encryptionType: LivekitModels.Encryption.Type) {
+    override fun onUserPacket(packet: LivekitModels.UserPacket, kind: LivekitModels.DataPacket.Kind, encryptionType: LivekitModels.Encryption.Type, participantIdentity: String) {
         val participant = getParticipantBySid(packet.participantSid) as? RemoteParticipant
         val data = packet.payload.toByteArray()
         val topic = if (packet.hasTopic()) {
@@ -1400,7 +1400,7 @@ constructor(
             null
         }
 
-        val event = RoomEvent.DataReceived(this, data, participant, topic, encryptionType)
+        val event = RoomEvent.DataReceived(this, data, participant, topic, encryptionType, participantIdentity)
         eventBus.postEvent(event, coroutineScope)
         participant?.onDataReceived(event)
     }

livekit-android-test/src/test/java/io/livekit/android/room/RoomDataMockE2ETest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 LiveKit, Inc.
+ * Copyright 2023-2026 LiveKit, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,7 @@ import livekit.LivekitModels.DataPacket
 import livekit.LivekitModels.UserPacket
 import livekit.org.webrtc.DataChannel
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
 import org.junit.Test
 import java.nio.ByteBuffer
 
@@ -62,4 +63,37 @@ class RoomDataMockE2ETest : MockE2ETest() {
         val event = events[0] as RoomEvent.DataReceived
         assertEquals("hello", event.data.decodeToString())
     }
+
+    @Test
+    fun dataReceivedReportsSenderIdentityWithoutParticipant() = runTest {
+        connect()
+        val subPeerConnection = component.rtcEngine().getSubscriberPeerConnection() as MockPeerConnection
+        val subDataChannel = MockDataChannel(RTCEngine.RELIABLE_DATA_CHANNEL_LABEL)
+        subPeerConnection.observer?.onDataChannel(subDataChannel)
+
+        val collector = EventCollector(room.events, coroutineRule.scope)
+        // Data sent by the Server API, or by a participant that has already left, has no
+        // RemoteParticipant in the room to attach to.
+        val dataPacket = with(DataPacket.newBuilder()) {
+            participantIdentity = "server-api-sender"
+            user = with(UserPacket.newBuilder()) {
+                payload = ByteString.copyFrom("hello", Charsets.UTF_8)
+                build()
+            }
+            build()
+        }
+        val dataBuffer = DataChannel.Buffer(
+            ByteBuffer.wrap(dataPacket.toByteArray()),
+            true,
+        )
+
+        subDataChannel.observer?.onMessage(dataBuffer)
+        val events = collector.stopCollecting()
+
+        assertEquals(1, events.size)
+        val event = events[0] as RoomEvent.DataReceived
+
+        assertNull(event.participant)
+        assertEquals("server-api-sender", event.participantIdentity)
+    }
 }