Example chat application using Nodejs + Socket.io

With Nodejs, we can create real-time application like chat-room. We can use Socket.io, WS or Websocket. Today, we introduce a simple chat application with Nodejs + Socket.io

Application structure:

chat nodejs socket io structure

File: package.json

     "name": "chat",
     "description": "example chat application with socket.io",
     "version": "0.0.1",
     "dependencies": {
        "express": "2.4.6",
        "socket.io": "0.8.4"

File: index.html

<script src="http://localhost:443/socket.io/socket.io.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
	var socket = io.connect('http://localhost:443');

	// on connection to server, ask for user's name with an anonymous callback
	socket.on('connect', function(){
		// call the server-side function 'adduser' and send one parameter (value of prompt)
		socket.emit('adduser', prompt("What's your name?"));

	// listener, whenever the server emits 'updatechat', this updates the chat body
	socket.on('updatechat', function (username, data) {
		$('#conversation').append('<b>'+username + ':</b> ' + data + '<br>');

	// listener, whenever the server emits 'updateusers', this updates the username list
	socket.on('updateusers', function(data) {
		$.each(data, function(key, value) {
			$('#users').append('<div>' + key + '</div>');

	// on load of page
		// when the client clicks SEND
		$('#datasend').click( function() {
			var message = $('#data').val();
			// tell server to execute 'sendchat' and send along one parameter
			socket.emit('sendchat', message);

		// when the client hits ENTER on their keyboard
		$('#data').keypress(function(e) {
			if(e.which == 13) {

<div style="float:left;width:100px;border-right:1px solid black;height:300px;padding:10px;overflow:scroll-y;">
	<div id="users"></div>
<div style="float:left;width:300px;height:250px;overflow:scroll-y;padding:10px;">
	<div id="conversation"></div>
	<input id="data" style="width:200px;" />
	<input type="button" id="datasend" value="send" />

File: app.js

var app = require('express').createServer();
var io = require('socket.io').listen(app);


// routing
app.get('/', function (req, res) {
  res.sendfile('index.html', {root: __dirname});

// usernames which are currently connected to the chat
var usernames = {};

io.sockets.on('connection', function (socket) {

	// when the client emits 'sendchat', this listens and executes
	socket.on('sendchat', function (data) {
		// we tell the client to execute 'updatechat' with 2 parameters
		io.sockets.emit('updatechat', socket.username, data);

	// when the client emits 'adduser', this listens and executes
	socket.on('adduser', function(username){
		// we store the username in the socket session for this client
		socket.username = username;
		// add the client's username to the global list
		usernames[username] = username;
		// echo to client they've connected
		socket.emit('updatechat', 'SERVER', 'you have connected');
		// echo globally (all clients) that a person has connected
		socket.broadcast.emit('updatechat', 'SERVER', username + ' has connected');
		// update the list of users in chat, client-side
		io.sockets.emit('updateusers', usernames);

	// when the user disconnects.. perform this
	socket.on('disconnect', function(){
		// remove the username from global usernames list
		delete usernames[socket.username];
		// update list of users in chat, client-side
		io.sockets.emit('updateusers', usernames);
		// echo globally that this client has left
		socket.broadcast.emit('updatechat', 'SERVER', socket.username + ' has disconnected');

Run: node app.js

Go to website: http://localhost:443/

chat nodejs socket io 1

chat nodejs socket io 2

Next tutorial: Example chat application using Nodejs + Websocket

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