I'm trying to make a peer to peer Javascript game that can be played on mobile browsers.
I've read that 80% to 90% of devices are able to connect over WebRTC without TURN servers so I am at a complete loss of what to do next.
Desktop: Google Chrome 79.0.3945.130 (Official Build) (64-bit) (cohort: Stable)
Mobile (Pixel 3/Android 10): Google Chrome 79.0.3945.116
MOBILE NETWORK
Time Event
1/24/2020, 11:58:17 PM createLocalDataChannel
label: Test, reliable: true
1/24/2020, 11:58:17 PM negotiationneeded
1/24/2020, 11:58:17 PM createOffer
1/24/2020, 11:58:17 PM createOfferOnSuccess
1/24/2020, 11:58:17 PM setLocalDescription
1/24/2020, 11:58:17 PM signalingstatechange
1/24/2020, 11:58:17 PM setLocalDescriptionOnSuccess
1/24/2020, 11:58:17 PM icegatheringstatechange
1/24/2020, 11:58:17 PM icecandidate (host)
1/24/2020, 11:58:17 PM icecandidate (srflx)
1/24/2020, 11:58:17 PM setRemoteDescription
1/24/2020, 11:58:17 PM addIceCandidate (host)
1/24/2020, 11:58:17 PM signalingstatechange
1/24/2020, 11:58:17 PM setRemoteDescriptionOnSuccess
1/24/2020, 11:58:17 PM iceconnectionstatechange
1/24/2020, 11:58:17 PM iceconnectionstatechange (legacy)
1/24/2020, 11:58:17 PM connectionstatechange
1/24/2020, 11:58:18 PM addIceCandidate (srflx)
1/24/2020, 11:58:33 PM iceconnectionstatechange
disconnected
1/24/2020, 11:58:33 PM iceconnectionstatechange (legacy)
failed
1/24/2020, 11:58:33 PM connectionstatechange
failed
WIFI NETWORK
Time Event
1/25/2020, 12:02:45 AM
createLocalDataChannel
label: Test, reliable: true
1/25/2020, 12:02:45 AM negotiationneeded
1/25/2020, 12:02:45 AM createOffer
1/25/2020, 12:02:45 AM createOfferOnSuccess
1/25/2020, 12:02:45 AM setLocalDescription
1/25/2020, 12:02:45 AM signalingstatechange
1/25/2020, 12:02:45 AM setLocalDescriptionOnSuccess
1/25/2020, 12:02:45 AM icegatheringstatechange
1/25/2020, 12:02:45 AM icecandidate (host)
1/25/2020, 12:02:45 AM icecandidate (srflx)
1/25/2020, 12:02:46 AM setRemoteDescription
1/25/2020, 12:02:46 AM signalingstatechange
1/25/2020, 12:02:46 AM setRemoteDescriptionOnSuccess
1/25/2020, 12:02:46 AM icegatheringstatechange
1/25/2020, 12:02:46 AM addIceCandidate (host)
1/25/2020, 12:02:46 AM iceconnectionstatechange
1/25/2020, 12:02:46 AM iceconnectionstatechange (legacy)
1/25/2020, 12:02:46 AM connectionstatechange
1/25/2020, 12:02:46 AM addIceCandidate (srflx)
1/25/2020, 12:02:46 AM iceconnectionstatechange
connected
1/25/2020, 12:02:46 AM iceconnectionstatechange (legacy)
connected
1/25/2020, 12:02:46 AM connectionstatechange
connected
1/25/2020, 12:02:46 AM iceconnectionstatechange (legacy)
completed
Peer to peer code
"use strict";
import { isAssetLoadingComplete } from '/game/assetManager.js';
import { playerInputHandler } from '/game/game.js';
const rtcPeerConnectionConfiguration = {
// Server for negotiating traversing NATs when establishing peer-to-peer communication sessions
iceServers: [{
urls: [
'stun:stun.l.google.com:19302'
]
}]
};
let rtcPeerConn;
// For UDP semantics, set maxRetransmits to 0 and ordered to false
const dataChannelOptions = {
// TODO: Set this to a unique number returned from joinRoomResponse
//id: 1,
// json for JSON and raw for binary
protocol: "json",
// If true both peers can call createDataChannel as long as they use the same ID
negotiated: false,
// TODO: Set to false so the messages are faster and less reliable
ordered: true,
// If maxRetransmits and maxPacketLifeTime aren't set then reliable mode will be on
// TODO: Send multiple frames of player input every frame to avoid late/missing frames
//maxRetransmits: 0,
// The maximum number of milliseconds that attempts to transfer a message may take in unreliable mode.
//maxPacketLifeTime: 30000
};
let dataChannel;
export let isConnectedToPeers = false;
export function createDataChannel(roomName, socket) {
rtcPeerConn = new RTCPeerConnection(rtcPeerConnectionConfiguration);
// Send any ice candidates to the other peer
rtcPeerConn.onicecandidate = onIceCandidate(socket);
// Let the 'negotiationneeded' event trigger offer generation
rtcPeerConn.onnegotiationneeded = function () {
console.log("Creating an offer")
rtcPeerConn.createOffer(sendLocalDesc(socket), logError('createOffer'));
};
console.log("Creating a data channel");
dataChannel = rtcPeerConn.createDataChannel(roomName, dataChannelOptions);
dataChannel.onopen = dataChannelStateOpen;
dataChannel.onmessage = receiveDataChannelMessage;
dataChannel.onerror = logError('createAnswer');
dataChannel.onclose = function(TODO) {
console.log(`Data channel closed for scoket: ${socket}`, TODO)
};
}
export function joinDataChannel(socket) {
console.log("Joining a data channel");
rtcPeerConn = new RTCPeerConnection(rtcPeerConnectionConfiguration);
rtcPeerConn.ondatachannel = receiveDataChannel;
// Send any ice candidates to the other peer
rtcPeerConn.onicecandidate = onIceCandidate(socket);
}
function receiveDataChannel(rtcDataChannelEvent) {
console.log("Receiving a data channel", rtcDataChannelEvent);
dataChannel = rtcDataChannelEvent.channel;
dataChannel.onopen = dataChannelStateOpen;
dataChannel.onmessage = receiveDataChannelMessage;
dataChannel.onerror = logError('createAnswer');
dataChannel.onclose = function(TODO) {
console.log(`Data channel closed for scoket: ${socket}`, TODO)
};
}
function onIceCandidate(socket) {
return function (event) {
if (event.candidate) {
console.log("Sending ice candidates to peer.");
socket.emit('signalRequest', {
signal: event.candidate
});
}
}
}
function dataChannelStateOpen(event) {
console.log("Data channel opened", event);
isConnectedToPeers = true;
if(!isAssetLoadingComplete) {
document.getElementById("startGameButton").textContent = "Loading...";
}
else {
document.getElementById('startGameButton').removeAttribute('disabled');
document.getElementById("startGameButton").textContent = "Start Game";
}
}
function receiveDataChannelMessage(messageEvent) {
switch(dataChannel.protocol) {
case "json":
const data = JSON.parse(messageEvent.data)
playerInputHandler(data);
break;
case "raw":
break;
}
}
export function signalHandler(socket) {
return function (signal) {
if (signal.sdp) {
console.log("Setting remote description", signal);
rtcPeerConn.setRemoteDescription(
signal,
function () {
// If we received an offer, we need to answer
if (rtcPeerConn.remoteDescription.type === 'offer') {
console.log("Offer received, sending answer")
rtcPeerConn.createAnswer(sendLocalDesc(socket), logError('createAnswer'));
}
},
logError('setRemoteDescription'));
}
else if (signal.candidate){
console.log("Adding ice candidate ", signal)
rtcPeerConn.addIceCandidate(new RTCIceCandidate(signal));
}
}
}
function sendLocalDesc(socket) {
return function(description) {
rtcPeerConn.setLocalDescription(
description,
function () {
console.log("Setting local description", description);
socket.emit('signalRequest', {
playerNumber: socket.id,
signal: description
});
},
logError('setLocalDescription'));
};
}
export function sendPlayerInput(playerInput){
dataChannel.send(JSON.stringify(playerInput));
}
function logError(caller) {
return function(error) {
console.log('[' + caller + '] [' + error.name + '] ' + error.message);
}
}
A TURN server is a solution to the problem. If there were workarounds that didn't require it, nobody would be using it. A common misconception here is that if you add a TURN server to the system, it will relay all traffic. That isn't true, it is only used as a fallback for the connections that can not be established otherwise. In comparison to the alternative of routing all your game messages through a websocket server this will still save you 80%+ of the traffic.
The next step is to install a TURN server. coturn is widely used and reasonably well documented. It is stable enough that, once setup, the amount of maintenance required is very low.