Establishing a WebRTC connection

Now that the signaling solution is in place, the final step is to establish a peer connection.

Continue editing the Program.cs file and append the following:

1. For debugging purpose, and to understand what is going on with the connection, connect the Connected and IceStateChanged events to handlers printing messages to console.

   pc.Connected += () => {
       Console.WriteLine("PeerConnection: connected.");
   };
   
   pc.IceStateChanged += (IceConnectionState newState) => {
       Console.WriteLine($"ICE state: {newState}");
   };
   

   The Connected event is invoked when the peer connection is established. The IceStateChanged is invoked each time the ICE status changes. Note that the Connected event can be invoked before the ICE status reaches its IceConnectionState.Connected state.

2. In order to verify that the remote video is received, we also subscribe to the I420AVideoFrameReady event. Since this event is invoked frequently, we only print a message every 60 frames.

   int numFrames = 0;
   pc.VideoTrackAdded += (RemoteVideoTrack track) => {
       track.I420AVideoFrameReady += (I420AVideoFrame frame) => {
           ++numFrames;
           if (numFrames % 60 == 0)
           {
               Console.WriteLine($"Received video frames: {numFrames}");
           }
       };
   };
   

3. To establish a WebRTC connection, one peer (the caller) has to call CreateOffer(), but not both (the callee just waits). Since the signaler implementation NamedPipeSignaler already provides a way to distinguish between the two peers, we use that information to select which peer will automatically initiate the call.

   if (signaler.IsClient)
   {
       Console.WriteLine("Connecting to remote peer...");
       pc.CreateOffer();
   }
   else
   {
       Console.WriteLine("Waiting for offer from remote peer...");
   }
   

4. In this state, the application is working but will terminate immediately once the peer connection is established. To prevent that, simply wait until the user press a key, and then close the signaler.

   Console.WriteLine("Press a key to terminate the application...");
   Console.ReadKey(true);
   signaler.Stop();
   Console.WriteLine("Program termined.");
   

Run the two instances of the application again. This time both terminals print a large quantity of messages related to SDP and ICE message exchanges, and eventually establish a WebRTC peer connection.

If launched with the audio or video capture flags, the capturer instance records those media and send them via the network to the other instance, which invokes the remote frame callback and print a message every 60 frames. After that, you can press any key to stop each instance. The signaler and peer connection will close and the program will terminate.