Node.js HTTP Module
Build a web server from scratch using Node's built-in http module — no framework required.
The Built-in http Module
Node.js ships with an http module that lets you create a fully functional web server without installing anything. It's the foundation every Node.js framework (Express, Koa, Fastify) is ultimately built on top of.
Creating a Server
http.createServer() takes a callback that runs once for every incoming request. The callback receives a request object (req) describing what the client asked for, and a response object (res) you use to send data back. Calling .listen() starts the server on a given port.
server.js
// server.js
const http = require("http");
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader("Content-Type", "text/plain");
res.end("Hello from Node.js!\n");
});
server.listen(3000, () => {
console.log("Server running at http://localhost:3000/");
});
// Run with: node server.js, then visit http://localhost:3000/Note: The server keeps the Node.js process alive on its own — you don't need a loop or a sleep call. As long as server.listen() is active, Node's event loop stays open waiting for connections.
Reading the Request: Method and URL
router.js
// router.js
const http = require("http");
const server = http.createServer((req, res) => {
res.setHeader("Content-Type", "application/json");
if (req.method === "GET" && req.url === "/") {
res.statusCode = 200;
res.end(JSON.stringify({ message: "Welcome home" }));
} else if (req.method === "GET" && req.url === "/about") {
res.statusCode = 200;
res.end(JSON.stringify({ message: "About this API" }));
} else {
res.statusCode = 404;
res.end(JSON.stringify({ error: "Not found" }));
}
});
server.listen(3000, () => console.log("Listening on port 3000"));- req.method — the HTTP verb: GET, POST, PUT, DELETE, etc.
- req.url — the requested path and query string, e.g. /about?ref=home.
- req.headers — an object containing the incoming request headers.
- res.statusCode / res.setHeader() / res.end() — control the outgoing response.
echo-server.js
// echo-server.js
const http = require("http");
const server = http.createServer((req, res) => {
if (req.method === "POST") {
let body = "";
req.on("data", (chunk) => (body += chunk));
req.on("end", () => {
res.statusCode = 200;
res.setHeader("Content-Type", "application/json");
res.end(JSON.stringify({ received: body }));
});
} else {
res.statusCode = 405;
res.end("Method Not Allowed");
}
});
server.listen(3000, () => console.log("Echo server on port 3000"));Note: Never leave a route unhandled without sending a response — if res.end() is never called, the client's connection hangs until it times out. Always make sure every code path terminates the response, including error cases.
Exercise: Node.js HTTP Module
Which built-in Node.js module is used to create a basic web server?
