Calculate client-server latency using socket.io

client.js

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

setInterval(function() {
  startTime = Date.now();
  socket.emit('client2server');
}, 2000);

socket.on('server2client', function() {
  latency = Date.now() - startTime;
  console.log(latency);
});

server.js

io.sockets.on('connection', function (socket) {
  socket.on('client2server', function() {
    socket.emit('pong');
  });
});

Changed the default: 'ping' and 'pong" event names to: 'client2server' and 'server2client'. Apparently 'ping' and 'pong' are already named events in socket io, and only trigger every 25 seconds.