expressjsHow can I use Express.js to implement websockets in my application?

Express.js is a web application framework for Node.js that can be used to implement websockets in your application. Websockets are a protocol for bi-directional communication between a server and a client.

To use Express.js to implement websockets, you will need to install the ws package.

npm install ws

Once the ws package is installed, you can create a websocket server using the WebSocket.Server class. This class takes an http.Server instance as an argument.

const http = require('http');
const express = require('express');
const WebSocket = require('ws');

const app = express();
const server = http.createServer(app);

const wss = new WebSocket.Server({ server });

The wss object will be an instance of WebSocket.Server that you can use to listen for events and send messages.

To listen for events, you can use the on method. This method takes two arguments: the name of the event and a callback function.

wss.on('connection', (ws) => {
  ws.on('message', (message) => {
    console.log(`Received message => ${message}`);
  });
});

To send a message, you can use the send method. This method takes a string as an argument.

wss.on('connection', (ws) => {
  ws.send('Hello World!');
});

Once you've set up the websocket server, you can start the server using the listen method.

server.listen(8080, () => {
  console.log('Listening on http://localhost:8080');
});

Output example

Listening on http://localhost:8080

Helpful links

• Express.js
• ws package
• WebSocket.Server class

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