Remarks
Socket.IO is a javascript library for realtime web applications. It enables realtime, bi-directional communication between web clients and servers. It has two parts: a client-side library that runs in the browser, and a server-side library for node.js. Both components have a nearly identical API. Like node.js, it is event-driven.
Socket.IO primarily uses the websocket protocol with polling as a fallback option,while providing the same interface. Although it can be used as simply a wrapper for webSocket, it provides many more features, including broadcasting to multiple sockets, storing data associated with each client, and asynchronous I/O.
Versions
| Version | Release Date |
|---|---|
| 1.4.8 | 2016-06-23 |
| 1.4.7 | 2016-06-23 |
| 1.4.6 | 2016-05-02 |
| 1.4.5 | 2016-01-26 |
| 1.4.4 | 2016-01-10 |
| 1.4.3 | 2016-01-08 |
| 1.4.2 | 2016-01-07 |
| 1.4.1 | 2016-01-07 |
| 1.4.0 | 2015-11-28 |
| 1.3.7 | 2015-09-21 |
| 1.3.6 | 2015-07-14 |
| 1.3.5 | 2015-03-03 |
| 1.3.4 | 2015-02-14 |
| 1.3.3 | 2015-02-03 |
| 1.3.2 | 2015-01-19 |
| 1.3.1 | 2015-01-19 |
| 1.3.0 | 2015-01-19 |
| 1.2.1 | 2014-11-21 |
| 1.2.0 | 2014-10-27 |
| 1.1.0 | 2014-09-04 |
| 1.0.6 | 2014-06-19 |
| 1.0.5 | 2014-06-16 |
| 1.0.4 | 2014-06-02 |
| 1.0.3 | 2014-05-31 |
| 1.0.2 | 2014-05-28 |
| 1.0.1 | 2014-05-28 |
| 1.0.0 | 2014-05-28 |
"Hello world!" with socket messages.
Install node modules
npm install express
npm install socket.io
Node.js server
const express = require('express');
const app = express();
const server = app.listen(3000,console.log("Socket.io Hello Wolrd server started!"));
const io = require('socket.io')(server);
io.on('connection', (socket) => {
//console.log("Client connected!");
socket.on('message-from-client-to-server', (msg) => {
console.log(msg);
})
socket.emit('message-from-server-to-client', 'Hello World!');
});
Browser client
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Hello World with Socket.io</title>
</head>
<body>
<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script>
<script>
var socket = io("http://localhost:3000");
socket.on("message-from-server-to-client", function(msg) {
document.getElementById('message').innerHTML = msg;
});
socket.emit('message-from-client-to-server', 'Hello World!');
</script>
<p>Socker.io Hello World client started!</p>
<p id="message"></p>
</body>
</html>
In the above example, the path to the socket.io library is defined as /socket.io/socket.io.js .
Even though we didn't write any code to serve the socket.io library, Socket.io automatically does that.
Installation or Setup
First, install socket.io module in node.js application.
npm install socket.io --save
Basic HTTP Setup
The following example attaches socket.io to a plain node.js HTTP server listening on port 3000.
var server = require('http').createServer();
var io = require('socket.io')(server);
io.on('connection', function(socket){
console.log('user connected with socketId '+socket.id);
socket.on('event', function(data){
console.log('event fired');
});
socket.on('disconnect', function(){
console.log('user disconnected');
});
});
server.listen(3000);
Setup with Express
Express app can be passed to http server which will be attached to socket.io .
var app = require('express')(); //express app
var server = require('http').createServer(app); //passed to http server
var io = require('socket.io')(server); //http server passed to socket.io
io.on('connection', function(){
console.log('user connected with socketId '+socket.id);
socket.on('event', function(data){
console.log('event fired');
});
socket.on('disconnect', function(){
console.log('user disconnected');
});
});
server.listen(3000);
Client Side Setup
Check the Hello World example above for the client side implementation.
