C# signaling

The C# library does not have a dedicated class for signaling. Instead, the PeerConnection class provides some events and methods to build upon in order to build a signaling solution.

A custom signaling solution needs to handle sending locally-prepared messages to the remote peer, for example via a separate TCP/IP connection, and dispatching messages received from the remote peer down to the local peer connection. Neither the WebRTC standard nor the MixedReality-WebRTC library specify the way those messages must be transmitted.

Local to remote

Local messages are generated under several circumstances by the local peer. The signaling solution must listen to the LocalSdpReadytoSend and IceCandidateReadytoSend events, and dispatch those messages to the remote peer by whatever way it choses.

peerConnection.LocalSdpReadyToSend += (string type, string sdp) => {
    MyCustomSignaling_SendSdp(type, sdp);
}

peerConnection.IceCandidateReadytoSend += (string candidate, int sdpMlineindex, string sdpMid) => {
    MyCustomSignaling_SendIce(candidate, sdpMlineindex, sdpMid);
}

Remote to local

Upon receiving the above messages, the signaling solution must:

• For SDP messages originating from a LocalSdpReadytoSend event invoked on the remote peer, call the PeerConnection.SetRemoteDescription() method to inform the local peer connection of the newly received session description.

  public void OnSdpMessage(string type, string sdp) {
      peerConnection.SetRemoteDescription(type, sdp);
      // Optionally
      if (type == "offer") {
          peerConnection.CreateAnswer();
      }
  }
  

• For ICE messages originating from an IceCandidateReadytoSend event invoked on the remote peer, call the PeerConnection.AddIceCandidate() method to inform the local peer connection of the newly received ICE candidate.

  public void OnIceMessage(string candidate, int sdpMlineindex, string sdpMid) {
      // Note the args order here!
      peerConnection.AddIceCandidate(sdpMid, sdpMlineindex, candidate);
  }