WebRTC RTCPeerConnection not established
<p>My simple WebRTC javascript-code does not work as intended. In fact, the audio-call does not get established (Note that I have minimum-knowledge of WebRTC, I created this by looking at examples on the internet). The page should initiate an audio call between two participants. As signaling-server between participants I used a websocket-server. This server only relays messages beetween participants. During the call-initiation messages are really sent (one offer, several candidates, one answer and other candidates) via websocket.<br>
Still, Firefox gives me "ICE failed, see about:webrtc for more details". Both participants are behind normal routers.<br>
I will add the log of my websocket-server and an example of about:webrtc (shortened, of course) as soon as possible.</p>

<p>Why does this code not work? What did I overlook?</p>

<p>My code is (have in mind this only works in firefox):</p>

<pre><code>ws = new WebSocket("ws://" + location.hostname + ":9000");
navigator.getUserMedia = function(a, b){ return navigator.mozGetUserMedia(a, b, error);};
offerOptions = {offerToRecieveAudio: 1, offerToRecieveVideo: 1};

var pc = new RTCPeerConnection({"iceServers": [
{url:'stun:stun.l.google.com:19302'},
{url:'stun:stunserver.org'},
]});
pc.onaddstream = function(obj) {
  if (obj.stream instanceof LocalMediaStream) return;
  var audio = document.createElement("audio");
  audio.controls = "true";
  audio.autoplay = "true";
  document.body.appendChild(audio);
  audio.srcObject = obj.stream;
}
pc.onicecandidate = function(evt){
        if (!evt.candidate) return;
        console.log(evt.candidate);
        ws.send(JSON.stringify(evt.candidate));
}

// Helper functions
function endCall() {
  var audios = document.getElementsByTagName("audio");
  for (var i = 0; i &lt; audios.length; i++) {
    audios[i].pause();
  }

  pc.close();
}

function error(err) {
  endCall();
}

function startCall(){
        navigator.getUserMedia({audio: true}, function(stream) {
        pc.onaddstream({stream: stream});
       pc.addStream(stream);

        pc.createOffer(function(offer) {
                pc.setLocalDescription(new RTCSessionDescription(offer),function() {
                ws.send(JSON.stringify(offer));
                }, error, offerOptions);
        }, error);
        });
}

ws.onmessage = function(message){
        var m = JSON.parse(message.data);
        console.log(m);

        if (m.type){
                if (m.type == "offer"){
                        navigator.getUserMedia({audio: true}, function(stream) {
                        pc.onaddstream({stream: stream});
                        pc.addStream(stream);

                        pc.setRemoteDescription(new RTCSessionDescription(m), function() {
                                pc.createAnswer(function(answer) {
                                pc.setLocalDescription(new RTCSessionDescription(answer), function() {
                                        ws.send(JSON.stringify(answer));
                                }, error);
                                }, error, offerOptions);
                        }, error);
                        });
                 }
                if (m.type == "answer"){
                        pc.setRemoteDescription(new RTCSessionDescription(m), function() { }, error);
                }
        }
        if (m.candidate){
                pc.addIceCandidate(new RTCIceCandidate(m));
        }
};
</code></pre>

<p>To initiate a call, you should only call the properly named <code>startCall()</code>-function.</p>

<p>The websocket-communication between two gives (ip's removed):</p>

<pre><code>Client connecting: tcp:ip1:62322
Client connecting: tcp:ip2:50075
Text message received: {"type":"offer","sdp":"v=0\r\no=mozilla...THIS_IS_SDPARTA-45.0.2 8467526262723029465 0 IN IP4 0.0.0.0\r\ns=-\r\nt=0 0\r\na=fingerprint:sha-256 8E:FC:F3:42:12:68:95:13:98:CC:B0:8D:41:F6:4E:39:19:60:70:5A:4B:4A:9D:93:4C:A0:53:CF:58:AB:3F:A1\r\na=ice-options:trickle\r\na=msid-semantic:WMS *\r\nm=audio 9 UDP/TLS/RTP/SAVPF 109 9 0 8\r\nc=IN IP4 0.0.0.0\r\na=sendrecv\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=ice-pwd:0a7123357b97345c6f9a9474aabf0c27\r\na=ice-ufrag:5d02cec2\r\na=mid:sdparta_0\r\na=msid:{512da0cd-689a-4981-9d88-9e857ba62803} {f7e81293-42b4-44e1-9d5b-80afe2857cf8}\r\na=rtcp-mux\r\na=rtpmap:109 opus/48000/2\r\na=rtpmap:9 G722/8000/1\r\na=rtpmap:0 PCMU/8000\r\na=rtpmap:8 PCMA/8000\r\na=setup:actpass\r\na=ssrc:2285633480 cname:{90d0392b-c8f1-4be9-af57-8c34d08567cd}\r\n"}
Text message received: {"candidate":"candidate:0 1 UDP 2122187007 localip2 51858 typ host","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:7 1 UDP 2122252543 ipv6-2 51859 typ host","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:0 2 UDP 2122187006 ip2 51860 typ host","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:7 2 UDP 2122252542 ipv6-2 52724 typ host","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:2 1 UDP 1685987327 ip2 51858 typ srflx raddr localip2 rport 51858","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:2 2 UDP 1685987326 ip2 51860 typ srflx raddr localip2 rport 51860","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"type":"answer","sdp":"v=0\r\no=mozilla...THIS_IS_SDPARTA-45.0.2 1868980908691513816 0 IN IP4 0.0.0.0\r\ns=-\r\nt=0 0\r\na=fingerprint:sha-256 04:2A:EB:AD:90:95:A3:A8:B8:3A:76:FE:3A:E7:DA:1F:D6:77:30:8A:87:BB:B9:3A:30:B4:9B:3D:E5:8F:58:04\r\na=ice-options:trickle\r\na=msid-semantic:WMS *\r\nm=audio 9 UDP/TLS/RTP/SAVPF 109\r\nc=IN IP4 0.0.0.0\r\na=sendrecv\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=ice-pwd:b5665ac44d79e66c392408e08bdc32ee\r\na=ice-ufrag:1a8f59a4\r\na=mid:sdparta_0\r\na=msid:{358aa02b-b035-41a8-acf6-2b787a192c60} {28e8765a-4a56-42e3-8f45-897ca7c99c05}\r\na=rtcp-mux\r\na=rtpmap:109 opus/48000/2\r\na=setup:active\r\na=ssrc:3277858225 cname:{8cee2fed-1a9e-46b9-90d7-3cad80050f3b}\r\n"}
Text message received: {"candidate":"candidate:0 1 UDP 2122252543 localip1 59706 typ host","sdpMid":"sdparta_0","sdpMLineIndex":0}
Text message received: {"candidate":"candidate:1 1 UDP 1686052863 ip1 59706 typ srflx raddr localip1 rport 59706","sdpMid":"sdparta_0","sdpMLineIndex":0}
</code></pre>