Creating a Basic HTTP Server with Node.js

Before Express existed, developers built HTTP servers with Node.js’s built-in http module. Express is a framework built directly on top of it. Understanding how the raw http module works — how requests arrive, how you read the URL and method, how you write a response — gives you a complete picture of what Express is actually doing on your behalf. In this lesson you will build a working HTTP server from scratch using only Node.js built-ins, see exactly why raw Node.js is cumbersome for an API, and appreciate the specific problems that Express solves.

What the http Module Provides #

Building a Raw HTTP Server #

// server-raw.js — a complete HTTP server using only built-in Node.js modules
const http = require('http');
const url  = require('url');

// In-memory data store (no MongoDB yet)
let posts = [
  { id: 1, title: 'First Post',  body: 'Hello MERN!' },
  { id: 2, title: 'Second Post', body: 'Node.js is great' },
];

const server = http.createServer(async (req, res) => {
  // Parse the URL to separate the path from query string
  const parsed   = url.parse(req.url, true);
  const pathname = parsed.pathname;
  const method   = req.method;

  // Set CORS and content-type headers on every response
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Content-Type', 'application/json');

  // ── Helper: read request body ─────────────────────────────────────────────
  function readBody() {
    return new Promise((resolve, reject) => {
      let body = '';
      req.on('data',  chunk => body += chunk.toString());
      req.on('end',   ()    => resolve(body));
      req.on('error', err   => reject(err));
    });
  }

  // ── Route: GET /api/health ────────────────────────────────────────────────
  if (pathname === '/api/health' && method === 'GET') {
    res.writeHead(200);
    res.end(JSON.stringify({ status: 'ok' }));
    return;
  }

  // ── Route: GET /api/posts ─────────────────────────────────────────────────
  if (pathname === '/api/posts' && method === 'GET') {
    res.writeHead(200);
    res.end(JSON.stringify({ success: true, data: posts }));
    return;
  }

  // ── Route: POST /api/posts ────────────────────────────────────────────────
  if (pathname === '/api/posts' && method === 'POST') {
    const raw  = await readBody();
    const body = JSON.parse(raw);
    const post = { id: posts.length + 1, ...body };
    posts.push(post);
    res.writeHead(201);
    res.end(JSON.stringify({ success: true, data: post }));
    return;
  }

  // ── 404 fallthrough ───────────────────────────────────────────────────────
  res.writeHead(404);
  res.end(JSON.stringify({ success: false, message: 'Route not found' }));
});

server.listen(5000, () => console.log('Raw HTTP server on http://localhost:5000'));

The Same API in Express — Side by Side #

// server-express.js — the same API with Express
const express = require('express');
const cors    = require('cors');
const app     = express();

let posts = [
  { id: 1, title: 'First Post',  body: 'Hello MERN!' },
  { id: 2, title: 'Second Post', body: 'Node.js is great' },
];

app.use(cors());          // CORS handled in one line
app.use(express.json());  // body parsing handled in one line

// Routes are clean, declarative, and easy to read
app.get('/api/health', (req, res) => res.json({ status: 'ok' }));

app.get('/api/posts', (req, res) => {
  res.json({ success: true, data: posts });
});

app.post('/api/posts', (req, res) => {
  const post = { id: posts.length + 1, ...req.body }; // body already parsed!
  posts.push(post);
  res.status(201).json({ success: true, data: post });
});

// 404 fallthrough
app.use((req, res) => res.status(404).json({ message: 'Route not found' }));

app.listen(5000, () => console.log('Express server on http://localhost:5000'));

What Express Removes #

Common Mistakes #

Mistake 1 — Not ending the response #

❌ Wrong — forgetting to call res.end() or res.json() hangs the request forever:

// Raw http
if (pathname === '/api/posts') {
  res.writeHead(200);
  // forgot res.end() — client waits forever, then times out
}

// Express
app.get('/api/posts', (req, res) => {
  const posts = getPosts();
  // forgot res.json(posts) — same problem
});

✅ Correct — every code path through a route handler must call a response method.

Mistake 2 — Not parsing the body in raw http #

❌ Wrong — reading req.body in raw Node.js http (it does not exist):

const server = http.createServer((req, res) => {
  const data = req.body; // undefined — body is a stream, not a property
  const post = JSON.parse(data); // TypeError: cannot parse undefined
});

✅ Correct — collect the stream manually (or just use Express which does this for you).

Mistake 3 — Confusing http.createServer with app.listen #

❌ Wrong assumption — thinking app.listen() is entirely separate from Node’s http module:

// Common misconception: Express.listen() is something special
// Reality:
app.listen(5000) === http.createServer(app).listen(5000)
// Express's app object IS the request handler passed to http.createServer()

✅ Understanding this matters when you add Socket.io — you need to pass the http server instance to Socket.io, not the Express app, which requires creating the http server explicitly.

Quick Reference #