server.js

const socket = new WebSocket("ws://<SERVER IP>:8765");


// Listen for messages
socket.addEventListener("message", (event) => {
  var enc = new TextDecoder("utf-8");
  event.data.arrayBuffer().then(buffer=>{
    var e = enc.decode(buffer);
	  console.log(e);
	  document.getElementById('remoteSessionDescription').value = e;
  });
});

let pc = new RTCPeerConnection({
  iceServers: [
    {
      urls: 'stun:stun.l.google.com:19302'
    }
  ]
})
let log = msg => {
  document.getElementById('div').innerHTML += msg + '<br>'
}

pc.ontrack = function (event) {
  var el = document.createElement(event.track.kind)
  el.srcObject = event.streams[0]
  el.autoplay = true
  el.controls = true

  document.getElementById('remoteVideos').appendChild(el)
}

pc.oniceconnectionstatechange = e => log(pc.iceConnectionState)
pc.onicecandidate = event => {
  if (event.candidate === null) {
    document.getElementById('localSessionDescription').value = btoa(JSON.stringify(pc.localDescription))
    socket.send(document.getElementById('localSessionDescription').value);
  }
}

// Offer to receive 1 audio, and 2 video tracks
pc.addTransceiver('audio', {'direction': 'recvonly'})
pc.addTransceiver('video', {'direction': 'recvonly'})
pc.addTransceiver('video', {'direction': 'recvonly'})
pc.createOffer().then(d => pc.setLocalDescription(d)).catch(log)

window.startSession = () => {
  let sd = document.getElementById('remoteSessionDescription').value
  if (sd === '') {
    return alert('Session Description must not be empty')
  }

  try {
    pc.setRemoteDescription(new RTCSessionDescription(JSON.parse(atob(sd))))
  } catch (e) {
    alert(e)
  }
}