Server-Sent Events alternative in Node.js - Mini Project: Build & Apply

Building a Server-Sent Events Alternative with Node.js and WebSockets

📖 Scenario: You want to create a simple real-time notification system for a website. Instead of using Server-Sent Events (SSE), you will use WebSockets, which allow two-way communication between the server and the browser.This project will guide you to build a basic Node.js server that sends messages to connected clients using WebSockets.

🎯 Goal: Build a Node.js server using the ws library that accepts WebSocket connections and sends a welcome message to each client when they connect.

📋 What You'll Learn

Create a WebSocket server using the ws library

Set up a port number variable for the server

Send a welcome message to each client when they connect

Close the connection properly when the client disconnects

💡 Why This Matters

🌍 Real World

WebSockets are widely used for real-time features like chat apps, live notifications, and gaming where the server needs to send updates instantly to the browser.

💼 Career

Understanding WebSocket servers is important for backend developers working on interactive web applications that require live data updates without refreshing the page.

1

Set up the WebSocket server

Create a constant called WebSocketServer by requiring the ws library, and create a new WebSocket server instance called wss without any options yet.

Node.js

// Your code here

Need a hint?

Use require('ws').Server to get the WebSocketServer class.

2

Configure the server port

Create a constant called PORT and set it to 8080 to define the port number where the WebSocket server will listen.

Node.js

const WebSocketServer = require('ws').Server;
const wss = new WebSocketServer({ noServer: true });

// Your code here

Need a hint?

Define PORT as 8080 to use a common port for WebSocket servers.

3

Send a welcome message on client connection

Add an event listener on wss for the 'connection' event with a callback that takes a ws parameter. Inside the callback, send the string 'Welcome to the WebSocket server!' to the connected client using ws.send().

Node.js

const WebSocketServer = require('ws').Server;
const wss = new WebSocketServer({ noServer: true });

const PORT = 8080;

// Your code here

Need a hint?

Use wss.on('connection', (ws) => { ... }) and inside send the welcome message with ws.send().

4

Start the server and handle client disconnect

Create a Node.js HTTP server using require('http').createServer() and listen on PORT. Upgrade HTTP connections to WebSocket connections by listening to the 'upgrade' event on the HTTP server and calling wss.handleUpgrade(). Also, inside the 'connection' event callback, add a listener for the 'close' event on ws that logs 'Client disconnected'.

Node.js

const WebSocketServer = require('ws').Server;
const wss = new WebSocketServer({ noServer: true });

const PORT = 8080;

wss.on('connection', (ws) => {
    ws.send('Welcome to the WebSocket server!');
    // Add close event listener here
});

// Create HTTP server and listen on PORT
// Add upgrade event listener to handle WebSocket connections
// Your code here

Need a hint?

Use http.createServer() to create the server and listen on PORT. Use server.on('upgrade', ...) to upgrade connections. Add ws.on('close', ...) inside the connection callback.