Node.js Fundamentals
Course 1 · Chapter 6 · HTTP Servers

🌐 HTTP Servers

The http module lets you create web servers in Node.js. Clients send HTTP requests to your server, and your server sends back HTTP responses. This chapter covers creating a basic HTTP server, handling requests, sending responses, parsing URLs, and routing requests to different handlers.

📡 HTTP Basics

HTTP is a request-response protocol:

Request

Client sends: method, URL, headers, body.

Response

Server sends: status code, headers, body.

Methods

GET (read), POST (create), PUT (update), DELETE (remove).

Status Codes

200 (OK), 404 (Not Found), 500 (Error), etc.

🏗️ Creating a Basic Server

const http = require('http');

const server = http.createServer((req, res) => {
  // req: the request object
  // res: the response object

  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello, World!');
});

server.listen(3000, 'localhost', () => {
  console.log('Server running at http://localhost:3000/');
});

Run with node server.js, then visit http://localhost:3000 in your browser.

📥 The Request Object

The req object contains information about the client's request:

const server = http.createServer((req, res) => {
  console.log('Method:', req.method);     // GET, POST, etc.
  console.log('URL:', req.url);           // /path?query=value
  console.log('Headers:', req.headers);   // {host, user-agent, ...}

  res.end('OK');
});

📤 The Response Object

Use the res object to send a response:

// Set status code
res.statusCode = 200;

// Set headers
res.setHeader('Content-Type', 'text/html');
res.setHeader('X-Custom-Header', 'value');

// Write body
res.write('
Hello
');
res.write('
World
');

// End response (required!)
res.end();

🛣️ Routing Requests

Handle different URLs differently:

const server = http.createServer((req, res) => {
  if (req.url === '/' && req.method === 'GET') {
    res.statusCode = 200;
    res.end('Home Page');
  } else if (req.url === '/about') {
    res.statusCode = 200;
    res.end('About Page');
  } else {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

🔍 Parsing Requests

Parse URL and Query Parameters

const { URL } = require('url');

const server = http.createServer((req, res) => {
  const url = new URL(req.url, `http://${req.headers.host}`);

  console.log('Pathname:', url.pathname);    // /search
  console.log('Query:', url.search);      // ?q=node

  const query = url.searchParams.get('q');
  console.log('Search query:', query);       // node

  res.end('OK');
});

📋 JSON Responses

const server = http.createServer((req, res) => {
  const data = {
    message: 'Hello, World!',
    timestamp: new Date()
  };

  res.setHeader('Content-Type', 'application/json');
  res.end(JSON.stringify(data));
});

📮 Handling POST Requests

const server = http.createServer(async (req, res) => {
  if (req.method === 'POST') {
    let body = '';

    // Collect request body
    req.on('data', chunk => {
      body += chunk.toString();
    });

    // Process when finished
    req.on('end', () => {
      const data = JSON.parse(body);
      console.log('Received:', data);

      res.setHeader('Content-Type', 'application/json');
      res.end(JSON.stringify({ success: true }));
    });
  }
});

📂 Serving Static Files

const fs = require('fs');
const path = require('path');

const server = http.createServer(async (req, res) => {
  const filePath = path.join(__dirname, 'public', req.url);

  try {
    const data = await fs.promises.readFile(filePath);
    res.statusCode = 200;
    res.end(data);
  } catch (error) {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

🔢 Common Status Codes

2xx Success

200 OK, 201 Created, 204 No Content

3xx Redirect

301 Moved, 302 Found, 304 Not Modified

4xx Client Error

400 Bad Request, 401 Unauthorized, 404 Not Found

5xx Server Error

500 Internal Error, 502 Bad Gateway, 503 Unavailable

💻 Coding Challenges

Challenge 1: Basic HTTP Server

Create a server that responds to /, /about, /api/users routes with different responses.

Goal: Learn server creation and basic routing.

→ Solution

Challenge 2: JSON API

Create a server that accepts GET/POST requests and responds with JSON data.

Goal: Handle requests and build a simple API.

→ Solution

Challenge 3: Serve Static Files

Create a server that serves HTML, CSS, and image files from a public directory.

Goal: Understand content types and static file serving.

→ Solution

💡 Server Best Practices

1. Always end responses: Call res.end() or data won't be sent.

2. Set correct content types: HTML, JSON, images need different MIME types.

3. Handle errors: Files might not exist, requests might be malformed.

4. Use Express later: For production, use frameworks like Express.js (we'll cover in exp1).

🎯 What's Next

You've created HTTP servers with Node.js! We'll explore more advanced topics, and soon move to Express.js — a powerful web framework that makes building servers much easier.