WebRTC-'RTCPeerConnection'：无法添加ICE候选对象

Question

The error I am getting in the browser console (only appears in chrome, no errors in firefox) is Error: Failed to execute 'addIceCandidate' on 'RTCPeerConnection': The ICE candidate could not be added.

I followed a tutorial and was able to get p2p video chat to work using nodejs. Now I am using Flask and python on the server side and angularjs on client side.

Signaling process for two peers is being done with angular-socketio.

console.log("The user connected to the socket");
socket.emit('readyToJoinRoom', {"signal_room": SIGNAL_ROOM});

//Send a first signaling message to anyone listening
//This normally would be on a button click

socket.emit('signal',{"type":"user_joined", "message":"Are you ready for a call?", "room":SIGNAL_ROOM});

socket.forward('signaling_message', $scope); 
$scope.$on('socket:signaling_message', function (ev, data) {
    displaySignalMessage("Signal received: " + data.type);
    // Setup the RTC Peer Connection object
    if (!rtcPeerConn) {
          startSignaling();
    }

    if(data.type != "user_joined") {
         console.log(data.message);
         var message = JSON.parse(data.message);
         console.log(message);
         if(message.sdp) {
             console.log("inside 2nd if statement");
             rtcPeerConn.setRemoteDescription(new RTCSessionDescription(message.sdp), function () {

             // if we received an offer, we need to answer
             if(rtcPeerConn.remoteDescription.type === 'offer') {
                  console.log("inside third if for remoteDescription."); // This never executes, error happens right before this line
                  rtcPeerConn.createAnswer(sendLocalDesc, logError);
             }
          }, logError);
  }
  else {
    console.log("addedddddddd ice candidate.");
    rtcPeerConn.addIceCandidate(new RTCIceCandidate(message.candidate));
  }    
 }
});

Once two people join the room the startSignaling() method is called. It sets the local description and completes 3 ice candidates then I receive an SDP but this is never true if(rtcPeerConn.remoteDescription.type === 'offer') even though it prints the SDP in the console with a type equal to offer. I am not sure why it never goes inside this if statement. I am not sure why I am getting an error. If you have any questions just ask. Thanks for the help.

Answer 1

I think

rtcPeerConn.setRemoteDescription(new RTCSessionDescription(message.sdp),...

will not work because the constructor of RTCSessionDescription needs the information about the type and the sdp. Try:

var desc = new RTCSessionDescription();
desc.sdp = message.sdp;
desc.type = "offer";
rtcPeerConn.setRemoteDescription(desc,.....

I had some issues constructing the RTCSessionDescription from JSON as well. Hope this helps...