ws library for WebSocket server in Node.js

Introduction

The ws library helps you create a WebSocket server easily. It lets your server and clients talk in real-time, like a chat app.

You want to build a chat app where messages appear instantly.

You need a live game server that updates players quickly.

You want to show live notifications or updates on a website.

You want to connect a dashboard to live data from a server.

Syntax

Node.js

import WebSocket, { WebSocketServer } from 'ws';

const wss = new WebSocketServer({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function message(data) {
    console.log('received: %s', data);
  });

  ws.send('Hello! Message from server');
});

Use WebSocketServer to create the server on a port.

Listen for connection events to handle new clients.

Examples

Creates a WebSocket server listening on port 3000.

Node.js

const wss = new WebSocketServer({ port: 3000 });

Sends a welcome message to each new client that connects.

Node.js

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

Logs any message received from a client.

Node.js

ws.on('message', message => {
  console.log('Client says:', message);
});

Sample Program

This code creates a WebSocket server on port 8080. When a client connects, it logs a message and sends a greeting. When the client sends a message, the server logs it and replies back with confirmation.

Node.js

import WebSocket, { WebSocketServer } from 'ws';

const wss = new WebSocketServer({ port: 8080 });

wss.on('connection', ws => {
  console.log('New client connected');

  ws.on('message', message => {
    console.log(`Received from client: ${message}`);
    ws.send(`Server got your message: ${message}`);
  });

  ws.send('Hello! You are connected to the server.');
});

Important Notes

Make sure the port you choose is open and not used by other apps.

Clients must use WebSocket protocol to connect (ws:// or wss://).

Use ws.send() to send messages to clients.

Summary

The ws library makes real-time communication easy.

Create a server with WebSocketServer and listen for connections.

Send and receive messages using ws.send() and message events.