How can I find the response time (latency) of a client in NodeJS with sockets (socket.io)?

Question

I\'m trying to create a multiplayer game with NodeJS and I want to synchronize the action between clients.

What would be the best way to find the latency (the time that

Answer 1

Overview:

After socket.io connection has been established, you create a new Date object on the client, let's call it startTime. This is your initial time before making a request to the server. You then emit a ping event from the client. Naming convention is totally up to you. Meanwhile server should be listening for a ping event, and when it receives the ping, it immediately emits a pong event. Client then catches the pong event. At this time you want to create another date object that represents Date.now(). So at this point you have two date objects - initial date before making a request to the server, and another date object after you make a request to the server and it replied. Subtract the startTime from current time and you have the latency.

Client

var socket = io.connect('http://localhost');
var startTime;

setInterval(function() {
  startTime = Date.now();
  socket.emit('ping');
}, 2000);

socket.on('pong', function() {
  latency = Date.now() - startTime;
  console.log(latency);
});

Server

io.sockets.on('connection', function (socket) {
  socket.on('ping', function() {
    socket.emit('pong');
  });
});

Also available as a Github Gist.