Integrate your Node.js and Express.js App with Socket.IO
Tags: programming, tutorial, node, community
Published: 2023-02-08 10:44:42


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## Introduction
Integrating Node.js, Express.js, and Socket.IO is required when creating real-time online applications. These technologies provide server-side web development projects with quick, scalable, and user-friendly solutions.

You will discover how to combine these technologies in this tutorial to create a real-time chat application.

## Prerequisites

- Basic knowledge of Node.js, Express.js and JavaScript.

- Node.js and npm installed on your machine.

## Step 1: Install dependencies
Before starting, install the essential dependencies, including Node.js, Express.js, and Socket.IO. Use npm to accomplish this:

```
npm install express socket.io
```

## Step 2: Set up a basic Express.js server
Your chat application will be built on a simple Express.js server that you create in this phase. The code below creates an HTTP server by calling require("http") on an Express.js server. Server (app), which listens on a certain port:

```
const express = require('express');
const app = express();
const server = require('http').Server(app);
const port = process.env.PORT || 3000;

server.listen(port, () => {
  console.log(`Server started on port ${port}`);
});
```

## Step 3: Integrate Socket.IO
You must incorporate Socket.IO if you want to provide your chat application real-time capabilities. Add the following code to your Express.js server to accomplish this:

```
const io = require('socket.io')(server);

io.on('connection', socket => {
  console.log('User connected');

  socket.on('disconnect', () => {
    console.log('User disconnected');
  });
});
```
By supplying the server to require("socket.io") in this case, io is constructed. When a client connects to the server, the code then waits for a "connection" event to be produced. The code logs a message to the console to show that a connection has been formed when one is made. A "disconnect" event is released when a user disconnects, and the code writes a message to the console to let the user know that they have disconnected.

## Step 4: Add chat functionality
You can now give your chat application conversation features after integrating Socket.IO. You can achieve this by issuing a chat message event to all connected clients after listening for a chat message event from the client.

```
io.on('connection', socket => {
  console.log('User connected');

  socket.on('chat message', message => {
    io.emit('chat message', message);
  });

  socket.on('disconnect', () => {
    console.log('User disconnected');
  });
});
```
Here, the code uses `socket.on('chat message', message => ... )` to monitor the client for a "chat message" event. The code utilizes the `io.emit()` function to send out a "chat message" event to all connected clients whenever a "chat message" event is received. In this manner, the message will be delivered to all connected clients, who will then be able to see it in the conversation.

## Conclusion
Now that Node.js, Express.js, and Socket.IO have been integrated, you have the ideal basis for a real-time online application. On top of this foundation, you can keep expanding and investigate the fascinating possibilities of real-time web development.

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