index.js

var express = require('express');
var app = express();
var path = require('path');
var server = require('http').createServer(app);
var io = require('socket.io')(server);
var port = 3000;

server.listen(port, function() {
  console.log('Server listening at port %d', port);
});

app.set('view engine', 'ejs');
app.use(express.static(path.join(__dirname, 'public')));

app.get('/', function(req, res) {
    res.render('pages/index');
});

var numUsers = 0;

io.on('connection', function(socket) {
  var addedUser = false;


  socket.on('new message', function(data) {

    socket.broadcast.emit('new message', {
      username: socket.username,
      message: data
    });
  });

  
  socket.on('add user', function(username) {
    if (addedUser) return;

    
    socket.username = username;
    ++numUsers;
    addedUser = true;
    socket.emit('login', {
      numUsers: numUsers
    });
    
    socket.broadcast.emit('user joined', {
      username: socket.username,
      numUsers: numUsers
    });
  });

  socket.on('typing', function() {
    socket.broadcast.emit('typing', {
      username: socket.username
    });
  });

  
  socket.on('stop typing', function() {
    socket.broadcast.emit('stop typing', {
      username: socket.username
    });
  });

  socket.on('disconnect', function() {
    if (addedUser) {
      --numUsers;

      socket.broadcast.emit('user left', {
        username: socket.username,
        numUsers: numUsers
      });
    }
  });
});