Handling connection events in Express - Mini Project: Build & Apply

Handling connection events

📖 Scenario: You are building a simple Express server that listens for client connections. You want to handle connection events to log when a client connects and disconnects.

🎯 Goal: Create an Express server that listens on port 3000 and logs messages when clients connect and disconnect.

📋 What You'll Learn

Create an Express app instance

Set up a server to listen on port 3000

Handle the 'connection' event on the server

Log a message when a client connects

Log a message when a client disconnects

💡 Why This Matters

🌍 Real World

Servers often need to know when clients connect or disconnect to manage resources or log activity.

💼 Career

Understanding connection events is important for backend developers working with network servers and real-time applications.

1

Create Express app and HTTP server

Create a variable called express that requires the 'express' module. Then create a variable called app by calling express(). Finally, create a variable called server by requiring the 'http' module and calling createServer(app).

Express

const express = require('express');
const app = express();
const http = require('http');
const server = http.createServer(app);
// Your code here

Need a hint?

Use require('express') to import Express. Then call express() to create the app. Use require('http') and createServer(app) to create the server.

2

Set the server to listen on port 3000

Add a line to make the server listen on port 3000 by calling server.listen(3000).

Express

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

// Make the server listen on port 3000
// Your code here

Need a hint?

Use server.listen(3000) to start the server on port 3000.

3

Handle the 'connection' event on the server

Add an event listener on server for the 'connection' event using server.on('connection', (socket) => { ... }). Inside the callback, log the message 'A client connected'.

Express

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

server.listen(3000);

// Add connection event listener
// Your code here

Need a hint?

Use server.on('connection', (socket) => { ... }) to listen for new connections and log a message inside the callback.

4

Log when a client disconnects

Inside the 'connection' event callback, add a listener on socket for the 'close' event using socket.on('close', () => { ... }). Inside this callback, log the message 'A client disconnected'.

Express

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

server.listen(3000);

server.on('connection', (socket) => {
  console.log('A client connected');
  // Add close event listener on socket
  // Your code here
});

Need a hint?

Inside the connection callback, use socket.on('close', () => { ... }) to detect when the client disconnects and log a message.