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Creating a Chat App Using NodeJS, ExpressJS, and Socket.IO

September 2, 2015

7:44 am

Socket.io is a trending library that allows bidirectional communication between client and server. It allows event-based communication between client and server with very less code. It works on every platform, a browser with good speed and reliability. Node.JS is the perfect technology for real-time applications like chat applications and expressjs is the most popular web framework in Node.JS.

Create an express application named chatApp

“`

$ express chatApp

create : chatApp

create : chatApp/package.json

create : chatApp/app.js

create : chatApp/public

create : chatApp/public/stylesheets

create : chatApp/public/stylesheets/style.css

create : chatApp/public/images

create : chatApp/routes

create : chatApp/routes/index.js

create : chatApp/routes/users.js

create : chatApp/views

create : chatApp/views/index.jade

create : chatApp/views/layout.jade

create : chatApp/views/error.jade

create : chatApp/bin

create : chatApp/bin/www

create : chatApp/public/javascripts

install dependencies:
$ cd chatApp && npm install

run the app:
$ DEBUG=chatApp ./bin/www

“`

Move to the application folder.

“`
$ cd chatApp/

“`
Just check the files created inside

“`
$ ls

“`
Now we need to install the dependencies. Dependencies are listed in the package.json. The current content of package.json file is

“`
{

“name”: “chatApp”,

“version”: “0.0.0”,

“private”: true,

“scripts”: {

“start”: “node ./bin/www”

},

“dependencies”: {

“express”: “~4.9.0”,

“body-parser”: “~1.8.1”,

“cookie-parser”: “~1.3.3”,

“morgan”: “~1.3.0”,

“serve-favicon”: “~2.1.3”,

“debug”: “~2.0.0”,

“jade”: “~1.6.0”

}

}

“`
To install the dependencies use the following command.

“`
$ npm install

“`

Now if you check the app.js file you can find lots of code. Remove everything and add the following code

var app = require(‘express’)();

var http = require(‘http’).Server(app);

http.listen(3000, function(){

console.log(‘listening on port:3000’);

});

Run the application using

“`
$ node app.js
“`
listening on port:3000

Create an index page with the following code and save the file with name index.html
<!DOCTYPE html>

<html>

<head>

<title>Chat App NodeJS+Socketio+ExpressJS</title>

</head>

<body>

Hello world

</body>

</html>

Now in the app.js we need to set the router for the index.html. For this add the following code inside the app.js
app.get(‘/’, function(req, res){

res.sendfile(‘index.html’);

});

$ node app.js

listening on port:3000

Now check the URL http://localhost:3000/

Now we need to install the socket.io. You can install socket.io using the following command

$ npm install –save socket.io

Now check the package.json and you can find that the socket.io is added to it with the version.

{

“name”: “chat”,

“version”: “0.0.0”,

“private”: true,

“scripts”: {

“start”: “node ./bin/www”

},

“dependencies”: {

“body-parser”: “~1.8.1”,

“cookie-parser”: “~1.3.3”,

“debug”: “~2.0.0”,

“express”: “~4.9.0”,

“jade”: “~1.6.0”,

“morgan”: “~1.3.0”,

“serve-favicon”: “~2.1.3”,

“socket.io”: “^1.3.5”

}

}

Add socket.io into HTML code using
<script src=”https://cdn.socket.io/socket.io-1.2.0.js”></script>
and update index.html with the following code
<script type=”text/javascript”>

var socket = io();

</script>

Update app.js with the following code
io.on(‘connection’, function(socket){

console.log(‘New client is connected to the server’);

});

Now update index.html with input box and send button
<!DOCTYPE html>

<html>

<head>

<title>Chat App NodeJS+Socketio+ExpressJS</title>

</head>

<body>

<ul id=”messages”></ul>

<form action=””>

<input id=”m” autocomplete=”off” /><button>Send</button>

</form>

<script src=”https://cdn.socket.io/socket.io-1.2.0.js”></script>

<script src=”http://code.jquery.com/jquery-1.11.1.js”></script>

<script type=”text/javascript”>

var socket = io();

var name = window.prompt(“What is your name?”);

socket.emit(‘login’, name);

$(‘form’).submit(function(){

socket.emit(‘sendMsg’,{by:name, msg: $(‘#m’).val()});

$(‘#m’).val(”);

return false;

});

socket.on(‘newUser’, function(name){

$(‘#messages’).append($(‘<li>’).text(name +” is online”));

});

socket.on(‘getMsg’, function(res){

$(‘#messages’).append($(‘<li>’).text(res.by +”: “+res.msg ));

});

</script>

</body>

</html>

Here we are creating a socket connection and emitting the message that the user type in the text box. We are getting the name of the user using the prompt. then sending a login event to server.

Now we need to listen to these events in server and handle them properly. So open the app.js file and update the io.connection function as:
io.on(‘connection’, function(socket){

console.log(‘New client is connected to the server’);

//listening to the sendMsg from client.
socket.on(‘sendMsg’, function(msg){

console.log(‘message: ‘ + msg);

//emiting the getMsg event to all the sockets that is connected.
io.emit(‘getMsg’, msg);

});

//Listening to the login event.
socket.on(“login”,function(name) {
//emitting the newUser event to all the clients
io.emit(‘newUser’, name);

});

});

Now in the command line type the following code. This will run our application
$ node app.js
Now open your browser and go to http://localhost:3000/ and enjoy the chat

Have questions? Contact the app development experts at InApp to learn more.

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