WebRTC onMessage() does not trigger on Android

Question

I have tried to implement datachannel on Android. I successfully send the data from android to web using datachannel.

However, whenever I try to send the data from the web to android, android doesn't receive the data and onMessage() is never triggered.

I don't understand why this happens. Here is how I implement DataChannel.Observer.

private class DcObserver implements DataChannel.Observer {
 // removed other overrided messages for clarity
 @Override
 public void onMessage(DataChannel.Buffer buffer) {
   Toast.makeText(getApplicationContext(),
                   "Some Data has been received", Toast.LENGTH_SHORT)
                   .show();
   Log.d("Data", "Some Data has been received");
 }
}

I create the object for every PeerConnection object. I have this class which contains the PeerConnection object.

private class FilePeer implements SdpObserver {
 private PeerConnection pc;
 private DataChannel dc;
 // removed other overrided methods for clarity
 public FilePeer() {
   PcObserver pcObserver = new PcObserver();

   pc = factory.createPeerConnection(RTCConfig.getIceServer(), 
       RTCConfig.getMediaConstraints(), pcObserver);

   dc = pc.createDataChannel("sendDataChannel", new DataChannel.Init());

    //DcObserver dcObserver = new DcObserver();

    //dc.registerObserver(dcObserver);    // This one crashes the app, therefore, getting the datachannel using onDataChannel
 }
}

This is how PcObserver class looks like.

private class PcObserver implements PeerConnection.Observer{

 @Override
 public void onDataChannel(final DataChannel dataChannel) {

  runOnUiThread(new Runnable() {
     public void run() {
         peer.dc = dataChannel;

         DcObserver dcObserver = new DcObserver();

         peer.dc.registerObserver(dcObserver);

         //dataChannel.registerObserver(dcObserver);
     }
   });
 }
 // other methods are removed for clarity
}

I think I am doing something wrong with peer.dc.registerObserver(dcObserver); But I don't know what.

Looks OK to me. The only think that's out of the ordinary is the fact that you're registering the observer on the UI thread. Why are you doing this? Can you try doing it directly in the `onDataChannel` method. — Svetlin Mladenov, Apr 18 '15 at 11:23
If I don't run it on UI thread then my application crashes. Maybe, a lot of work is happening. I have found the solution and will post the answer for this. — SamFast, Apr 18 '15 at 12:23

score 1 · Accepted Answer · answered Apr 18 '15 at 12:28

I found the solution for this problem on webrtc group.

I need to hold on to a reference of the observer to make sure it does not get destroyed when the DataChannel calls back.

One more thing, we need to do is remove peer.dc = dataChannel; inside onDataChannel();,

The following code works fine for me now:

    public void onDataChannel(final DataChannel dataChannel) {
        final DataChannel dc = dataChannel;
        runOnUiThread(new Runnable() {
              public void run() {

                    DcObserver dcObserver = new DcObserver();

                    peer.dc.registerObserver(dcObserver);

              }
            });


    }

WebRTC onMessage() does not trigger on Android

1 Answers1