Socket.io for beginners
Published: 2023-02-04 12:34:07

This [post was first published on my blog](https://levelup.gitconnected.com/beginners-guide-to-socket-io-6161157fc3b9). If you want to know more details, read my blog:
https://levelup.gitconnected.com/beginners-guide-to-socket-io-6161157fc3b9

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Socket.IO is a JavaScript library that enables real-time, bidirectional communication between clients and servers. It allows you to create web applications that can handle a high volume of concurrent connections and enables you to build real-time features such as chat, notifications, and collaborative editing. In this article, we'll give you a brief introduction to Socket.IO and how it works. We'll also discuss some of the key features of the library and show you how to get started with Socket.IO in your own projects.
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**Definition**
As mentioned in the beginning, Socket.IO is a JavaScript library that enables real-time, bidirectional communication between clients and servers. It allows you to create web applications that can handle a high volume of concurrent connections and enables you to build real-time features such as chat, notifications, and collaborative editing.
Features
Some of the key features of Socket.IO are:
Real-time, bidirectional communication between clients and servers: Socket.IO enables you to send and receive data in real time between the client and server.
Cross-platform compatibility: Socket.IO can be used to build real-time applications for the web, mobile devices, and desktop applications.
Automatic reconnection: Socket.IO will automatically try to reconnect if the connection is lost, making it easy to build highly available real-time applications.
Event-based communication: Socket.IO uses an event-based model for communication, where the client and server can emit and listen for events. This makes it easy to build real-time features such as chat, notifications, and collaborative editing.
Fallback transports: Socket.IO can use WebSockets or fall back to other techniques such as long-polling if WebSockets are not available. This makes it easy to use Socket.IO in a wide variety of environments.
Binary support: Socket.IO can send and receive binary data, making it easy to build real-time applications that transfer files or other binary data.
Namespaces: Socket.IO allows you to divide your application into multiple "namespaces", each with its own set of connections and events. This can be useful for organizing your real-time application into logical components.

**Functionality**
Socket.IO uses a combination of WebSockets, polling, and other technologies to enable real-time communication. When a client (such as a web browser) wants to establish a connection with the server, Socket.IO establishes a WebSocket connection if the browser supports it. If the browser does not support WebSockets, Socket.IO falls back to other techniques such as long-polling to establish a connection.
We wrote an article about WebSockets here already.
Long polling works by having the client send a request to the server, and then the server keeps the request open until it has new data to send back to the client. Once the server has new data, it sends a response to the client and the client sends a new request immediately. This process is repeated, allowing the client and server to communicate in real-time.
One of the main drawbacks of long polling is that it requires a new HTTP request-response cycle for each piece of data that is exchanged between the client and server. This can result in increased latency and reduced efficiency compared to WebSockets. However, long polling can be a good choice in certain situations, such as when the client and server need to communicate over HTTP rather than a dedicated WebSocket connection.
Once the connection is established, the client and server can send data to each other in real time. Socket.IO uses an event-based model for communication, where the client and server can emit and listen for events. For example, the client might emit a "message" event with some data, and the server could listen for that event and respond by emitting a "response" event with some data of its own.
Socket.IO is a popular choice for building real-time web applications because it abstracts away the complexities of real-time communication and provides a simple, easy-to-use API. It is also cross-platform, meaning it can be used to build real-time applications for the web, mobile devices, and desktop applications.

**Example**
To get started with Socket.IO in your own projects, you'll need to do the following:
Install the Socket.IO library: You can install Socket.IO using npm or yarn by running npm install socket.io or yarn add socket.io. Alternatively, you can include the Socket.IO client library in your HTML file by adding a script tag to your HTML file: <script src="/socket.io/socket.io.js"></script>
Set up the server: On the server side, you'll need to set up Socket.IO to listen for incoming connections. Here's an example of how you might set up Socket.IO with an express server in Node.js:

const express = require('express');
const app = express();
const server = require('http').Server(app);
const io = require('socket.io')(server);
server.listen(3000);
Set up the client: On the client side, you'll need to create a Socket.IO client and connect to the server. Here's an example of how you might do this in JavaScript:

const socket = io('http://localhost:3000');
Send and receive events: Once the client is connected to the server, you can use the emit and on methods to send and receive events. For example, the client can emit a "message" event with some data, and the server can listen for that event and respond by emitting a "response" event with some data of its own:

// On the client:
socket.emit('message', 'Hello, server!');
// On the server:
io.on('connection', (socket) => {
  socket.on('message', (data) => {
    console.log(data); // 'Hello, server!'
    socket.emit('response', 'Hello, client!');
  });
});

That's the basic idea! With these steps, you should be able to get started with Socket.IO in your own projects. There are many more advanced features and configurations available in Socket.IO, so be sure to check out the documentation for more information

We hope you enjoyed this article. Do you have any questions? Let us know and comment below.

For more details you can read them on my blog:
https://levelup.gitconnected.com/beginners-guide-to-socket-io-6161157fc3b9