server.js

var express = require('express');
var app = express();
var http = require('http').Server(app);
var io = require('socket.io')(http);

//Enable CORS 
// app.use(function(req, res, next) {
//     res.header("Access-Control-Allow-Origin", "*");
//     res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
//     res.header("Access-Control-Allow-Methods", "GET,PUT,POST,DELETE");
//     next();
// });

//Store user data in variable room
var rooms = [];

//Get Room id from url
app.get('/:roomName', function(req, res) {

    activeChat = req.params.roomName;
    res.sendFile(__dirname + '/public/chat.html');

});
app.get('/:roomName/', function(req, res) {

    activeChat = req.params.roomName;
    res.sendFile(__dirname + '/public/chat.html');

});

app.use(express.static(__dirname + '/public/'));

//Socket.io on connection event

io.on('connection', function(socket) {
    /*Check if the socket was already connected previously
      .user .room custom properties are added to the on connection. 
      In cases when server fails and restarts 
    */

    if (socket.user === undefined || socket.room === undefined)
        io.to(socket.id).emit("giveuser");

    //User disconnect event listener.
    socket.on('disconnect', function() {
        /*  Code:
            Remove user from socket.
            Search user in it's room and remove it from user array of the room.
            If room is empty, remove the room.
    */
        socket.leave(socket.room);
        var user_idx = -1;

        //Check if user room is lost. Common cause: Server restart. 
        if (rooms[socket.room] != undefined) {
            for (var i = 0; i < rooms[socket.room].user_array.length; i++) {
                if (rooms[socket.room].user_array[i][0] === socket.user) {
                    //Find user in user array. O(length)
                    user_idx = i;
                    break;
                }
            }

            //Remove user from user_array.
            rooms[socket.room].user_array.splice(user_idx, 1);

            if (rooms[socket.room].user_array.length === 0) {
                delete rooms[socket.room];
            }

            //Update people online for other users.
            io.sockets.in(socket.room).emit('user_disconnect', socket.user);

            console.log(socket.user + " disconnected.");
        } else
            console.log("Probable Server Restart. Disconnecting user to reconnect. user: %s room: %s", socket.user, socket.room);

    });

    socket.on('addToRoom', function(roomName) {
        /*  Code:
            Add user to room.
            Add custom property .user .room to socket for later identification.
            Search if room exists. Add user.
    */

        socket.room = roomName.room;
        socket.user = roomName.user;

        var flag = 0; //NOTE: No race conditions observed now

        for (var key in rooms) {
            if (key === socket.room) {
                flag = 1;
                break;
            }
        }

        if (flag === 0) {
            rooms[socket.room] = {
                name: socket.room,
                user_array: []
            }
            rooms[socket.room].user_array.push([socket.user, socket.id]);
        } else {
            rooms[socket.room].user_array.push([socket.user, socket.id]);
        }

        //Add socket to provided room
        socket.join(socket.room);

        //Send user_connect msg to other users in room.
        io.sockets.in(socket.room).emit('user_connect', rooms[socket.room].user_array);

        console.log(socket.user + " connected.");
    });

    //Broadcast users chat message to its room.
    socket.on('chatmsg', function(msg) {
        socket.broadcast.to(socket.room).emit('chatmsg', {
            "user": socket.user,
            "msg": msg
        });
    });

    socket.on('usertyping', function(user) {
        socket.broadcast.to(socket.room).emit('usertyping', user);
    });
});
    http.listen((process.env.PORT || 5000), function() {
        console.log('Server running');
    });