HTTP server basics

Node ships node:http to create HTTP servers without third-party frameworks. Every Express app ultimately sits on the same primitives—understanding them clarifies routing, headers, and status codes.

Minimal server

import http from 'node:http';

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello\n');
});

server.listen(3000);

Request object

req.method, req.url, and headers describe the incoming request. You must read the body from req streams for POST data—frameworks parse this for you.

Playground pattern

The runner uses a short-lived server: listen on port 0 (OS picks a free port), log, then close() and process.exit(0) so the sandbox finishes cleanly.

Important interview questions and answers

1. Q: What does res.writeHead do?
   A: Sends status code and response headers before the body—must happen before res.end for that response.
2. Q: HTTP vs HTTPS in Node?
   A: node:https module with TLS certificates—often terminated at a load balancer in production.

Self-check

1. Which module creates a bare HTTP server?
2. Why close the server in playground demos?