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Step 1: Raw HTTP Server

What You'll Learn

How to build a web server from scratch using only Node.js—without Express or any framework.

Big Picture

Every web service starts as a Node.js HTTP server. It:

  1. Listens for requests from clients
  2. Parses the incoming data
  3. Runs some logic
  4. Sends back a response

This step teaches you exactly how each of these works.

What To Build

An HTTP server that:

  • Accepts POST /tasks requests with JSON data
  • Returns GET /tasks to list all tasks
  • Uses manual routing (no framework helps you)
  • Parses request bodies from stream chunks
  • Sends proper HTTP status codes

Why This Matters

Frameworks like Express do all this automatically. But when things go wrong in production:

  • You need to debug the lowest level
  • You need to understand how bodies are parsed
  • You need to know why a request might hang

Knowing the raw server means you can diagnose any issue.

Real Example in Your Code

All routing lives in server.js at the top. Look for the createServer() function.

Key parts:

  • http.createServer(async (req, res) => {...}) — creates the server
  • req.url and req.method — tells you what request arrived
  • req.on('data', chunk => {...}) — receives body in parts
  • res.writeHead(200, { 'Content-Type': 'application/json' }) — sets response headers
  • res.end(JSON.stringify(data)) — sends the response

How Request Bodies Work

When a client sends data (like POST with JSON), it arrives in chunks, not all at once.

Think of it like mail:

  • Chunk 1: envelope arrives
  • Chunk 2: first page of letter
  • Chunk 3: second page
  • Chunk 4: signature

Buffer all chunks, wait for end, then parse.

Example flow:

let body = "";
req.on("data", (chunk) => {
  body += chunk; // Accumulate pieces
});
req.on("end", () => {
  const data = JSON.parse(body); // Parse when complete
});

If you parse before end fires, you get incomplete data. ✗

Common Mistakes

❌ Mistake 1: Assuming body arrives all at once
✓ Fix: Always listen to data and end events

❌ Mistake 2: Not handling parse errors
✓ Fix: Wrap JSON.parse in try/catch

❌ Mistake 3: Wrong response headers
✓ Fix: Always set Content-Type: application/json

❌ Mistake 4: Updating request body stream without buffering
✓ Fix: Buffer everything first, parse second

Your Turn: Build It

Task: Add a new endpoint GET /health

Requirements:

  • Return { status: "ok", uptime: process.uptime() }
  • Status code: 200
  • Content-Type: application/json
  • Do NOT use Express or any external library

Hints:

  • Add a new if statement checking req.url and req.method
  • Use res.writeHead() to set headers
  • Use res.end() to send the response

Test it:

curl http://localhost:3000/health

Real-World Connection

Production incidents often trace back to:

  • Wrong status code sent (500 instead of 400)
  • Malformed response JSON
  • Not handling network disconnections
  • Request body timeouts

Understanding raw servers helps you:

  • Spot issues faster
  • Design better error pages
  • Handle edge cases in production

Next Step

The server is just infrastructure. Next, you'll learn how to store and retrieve data using a Hash Map.

→ Step 2: In-Memory Storage