How does the HTTP module work in Node.js?

The HTTP Module

The http module is a core Node.js module that allows you to create HTTP servers and make HTTP requests without any external dependencies. It's the foundation upon which frameworks like Express.js are built.

Creating an HTTP Server

const http = require('http');

const server = http.createServer((req, res) => {
  // req = IncomingMessage (readable stream)
  // res = ServerResponse (writable stream)

  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({ message: 'Hello World' }));
});

server.listen(3000, () => {
  console.log('Server running on port 3000');
});

Request Object (IncomingMessage)

const server = http.createServer((req, res) => {
  console.log(req.method);     // GET, POST, PUT, DELETE
  console.log(req.url);        // /api/users?page=1
  console.log(req.headers);    // { host: '...', 'content-type': '...' }

  // Parse URL
  const url = new URL(req.url, `http://${req.headers.host}`);
  console.log(url.pathname);    // /api/users
  console.log(url.searchParams.get('page')); // '1'
});

Handling POST Body

The request body arrives as a stream — you must collect chunks:

const server = http.createServer((req, res) => {
  if (req.method === 'POST' && req.url === '/api/users') {
    let body = '';

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

    req.on('end', () => {
      const data = JSON.parse(body);
      res.writeHead(201, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({ created: data }));
    });
  }
});

Simple Router

const server = http.createServer((req, res) => {
  const { method, url } = req;

  if (method === 'GET' && url === '/') {
    res.writeHead(200, { 'Content-Type': 'text/html' });
    res.end('<h1>Home</h1>');
  } else if (method === 'GET' && url === '/api/users') {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify([{ id: 1, name: 'John' }]));
  } else {
    res.writeHead(404, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ error: 'Not Found' }));
  }
});

Making HTTP Requests

const http = require('http');

// GET request
http.get('http://api.example.com/data', (res) => {
  let data = '';
  res.on('data', (chunk) => data += chunk);
  res.on('end', () => console.log(JSON.parse(data)));
});

// POST request
const postData = JSON.stringify({ name: 'John' });
const options = {
  hostname: 'api.example.com',
  port: 80,
  path: '/users',
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Content-Length': Buffer.byteLength(postData)
  }
};

const req = http.request(options, (res) => {
  let data = '';
  res.on('data', (chunk) => data += chunk);
  res.on('end', () => console.log(JSON.parse(data)));
});

req.write(postData);
req.end();

http vs https vs http2

Module	Protocol	Use Case
`http`	HTTP/1.1	Development, internal services
`https`	HTTPS (TLS)	Production, public APIs
`http2`	HTTP/2	Performance (multiplexing, server push)

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

const server = https.createServer({
  key: fs.readFileSync('key.pem'),
  cert: fs.readFileSync('cert.pem')
}, (req, res) => {
  res.writeHead(200);
  res.end('Secure!');
});

Why Use Express Instead?

Feature	Raw http	Express.js
Routing	Manual if/else	`app.get('/path')`
Body parsing	Manual stream handling	Built-in middleware
Middleware	No built-in support	First-class support
Static files	Manual	`express.static()`

Tip: Understanding the raw http module helps you understand what Express does under the hood. In production, use Express or Fastify for developer productivity, but know the fundamentals.

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