script.js

let room;
let pc;

function onSuccess() {};
function onError(error) {
  console.error(error);
};
// Send signaling data via Scaledrone
function sendMessage(message) {
  drone.publish({
    room: roomName,
    message
  });
}

function startWebRTC(isOfferer) {
  pc = new RTCPeerConnection(configuration);

  // 'onicecandidate' notifies us whenever an ICE agent needs to deliver a
  // message to the other peer through the signaling server
  pc.onicecandidate = event => {
    if (event.candidate) {
      sendMessage({'candidate': event.candidate});
    }
  };

  // isOfferer == member.length === 2, i.e. there are 2 people in the room
  if (isOfferer) {
    pc.onnegotiationneeded = () => {
      pc.createOffer().then(localDescCreated).catch(onError);
    }
  }

  // Display the remote video stream in the #remoteVideo element
  pc.onaddstream = event => {
    remoteVideo.srcObject = event.stream;
  };

  navigator.mediaDevices.getUserMedia({
    audio: true,
    video: true,
  }).then(stream => {
    // Display your local video in #localVideo element
    localVideo.srcObject = stream;
    // Add your stream to be sent to the other peer
    pc.addStream(stream);
  }, onError);

  // Listen to signaling data from Scaledrone
  room.on('data', (message, client) => {
    // If the message was sent by us
    if (client.id === drone.clientId) {
      return;
    }

    if (message.sdp) {
      //When you're the 2nd person
      //This is called after receiving an offer or answer from another peer
      pc.setRemoteDescription(new RTCSessionDescription(message.sdp), () => {
        // When receiving an offer let's answer it
        if (pc.remoteDescription.type === 'offer') {
          pc.createAnswer().then(localDescCreated).catch(onError);
        }
      }, onError);
    } else if (message.candidate) {
      //When you're the 1st one
      //Add the new ICE candidate to our connections remote description
      pc.addIceCandidate(
        new RTCIceCandidate(message.candidate), onSuccess, onError
      );
    }
  });
}

function localDescCreated(desc) {
  pc.setLocalDescription(
    desc,
    () => sendMessage({'sdp': pc.localDescription}),
    onError
  );
}

//-------------------  main code -----------------------
//Using google's public STUN server
//Using ScaleDrone's server as signaling server
//Using RTCPeerConnection, getUserMedia API
// Generate random room name if needed
if (!location.hash) {
  location.hash = Math.floor(Math.random() * 0xFFFFFF).toString(16);
}
const roomHash = location.hash.substring(1);

// Our own channel ID registered in ScaleDrone
const drone = new ScaleDrone('lThnE5uuEod3c5cI');
// Room name needs to be prefixed with 'observable-'
const roomName = 'observable-' + roomHash;
// Using google's public STUN Server
const configuration = {
  iceServers: [{
    urls: 'stun:stun.l.google.com:19302'
  }]
};

//Subscribe a roomName in ScaleDrone
drone.on('open', error => {
  if (error) {
    return console.error(error);
  }
  room = drone.subscribe(roomName);
  room.on('open', error => {
    if (error) {
      onError(error);
    }
  });
  // Connect to the room and received an array of 'members'
  // Signaling server is ready.
  room.on('members', members => {
    console.log('MEMBERS', members);
    // If we are the second user to connect to the room we will be creating the offer
    const isOfferer = members.length === 2;
    startWebRTC(isOfferer);
  });
});
//-------------------------------------------------------