Modern WebRTC find turn selected

by jib1

HTML

<video id="v1" width="108" height="81" autoplay></video>
<video id="v2" width="108" height="81" autoplay></video><br>
<button onclick="start()">Start!</button><br><div id="div"></div>
<script src="https://webrtc.github.io/adapter/adapter-latest.js"></script>

JavaScript

// Turn server is on Mozilla's VPN. Replace with your own.
var cfg = { iceTransportPolicy: "all", // set to "relay" to force TURN.
            iceServers: [{ urls: "stun:stun.l.google.com:19302" },
                         { urls: "turn:10.252.73.50",
                           username:"webrtc", credential:"firefox" }] };
var pc1 = new RTCPeerConnection(cfg), pc2 = new RTCPeerConnection(cfg);

var add = (pc, can) => can && pc.addIceCandidate(can).catch(log);
pc1.onicecandidate = e => add(pc2, e.candidate);
pc2.onicecandidate = e => add(pc1, e.candidate);
pc2.oniceconnectionstatechange = () => log(pc2.iceConnectionState);
pc2.onaddstream = e => v2.srcObject = e.stream;

var findSelected = stats =>
  [...stats.values()].find(s => s.type == "candidate-pair" && s.selected);

var start = () => navigator.mediaDevices.getUserMedia({ video: true })
  .then(stream => pc1.addStream(v1.srcObject = stream))
  .then(() => pc1.createOffer()).then(d => pc1.setLocalDescription(d))
  .then(() => pc2.setRemoteDescription(pc1.localDescription))
  .then(() => pc2.createAnswer()).then(d => pc2.setLocalDescription(d))
  .then(() => pc1.setRemoteDescription(pc2.localDescription))
  .then(() => waitUntil(() => pc1.getStats().then(s => findSelected(s))))
  .then(() => pc1.getStats())
  .then(stats => {
    var candidate = stats.get(findSelected(stats).localCandidateId);
    if (candidate.candidateType == "relayed") {
      log("Uses TURN server: " + candidate.ipAddress);
    } else {
      log("Does not use TURN (uses " + candidate.candidateType + ").");
    }
  })
  .catch(log);

var waitUntil = f => Promise.resolve(f())
  .then(done => done || wait(200).then(() => waitUntil(f)));

var wait = ms => new Promise(resolve => setTimeout(resolve, ms));
var log = msg => div.innerHTML += msg +"<br>";