Node.js HTTP Server

What you will practice

• Create a server with `node:http`.
• Return plain text and JSON responses.
• Understand request URL, method, status code, and headers.

What this means

A Node.js server is a long-running process that listens for HTTP requests.

The built-in `node:http` module can create a server without Express or any third-party framework.

Every request has a method and URL. Every response should have a status code, headers, and a body.

Mini glossary

HTTP server

A program that listens for HTTP requests and sends HTTP responses.

Request

Incoming data from a client, including method and URL.

Response

The status code, headers, and body sent back to the client.

How it works step by step

1. Create `server.js` and import `createServer` from `node:http`.
2. Inside the request handler, inspect `req.url` and `req.method`.
3. Set `statusCode` and `Content-Type` before ending the response.
4. Run `node server.js`, then test the server from another terminal with `curl`.

Where you will use this

• A health endpoint returns `ok` for uptime checks.
• A JSON API returns tool data to a frontend.
• A webhook endpoint receives events from another service.

Before you run the code

This lesson intentionally starts with built-in Node.js. Frameworks such as Express are easier to appreciate after you see the raw request/response model.

Stop the server with `Ctrl+C` when you are done.

Run it locally

These examples are meant for a local Node.js project. Create the files shown below, then run the terminal commands from the project folder.

mkdir lumio-http-demo
cd lumio-http-demo
touch server.js

const { createServer } = require("node:http");

const hostname = "127.0.0.1";
const port = Number(process.env.PORT || 3000);

const tools = [
  { id: "json-formatter", title: "JSON Formatter" },
  { id: "http-status-code-reference", title: "HTTP Status Code Reference" }
];

const server = createServer((req, res) => {
  if (req.method === "GET" && req.url === "/health") {
    res.statusCode = 200;
    res.setHeader("Content-Type", "text/plain; charset=utf-8");
    res.end("ok");
    return;
  }

  if (req.method === "GET" && req.url === "/api/tools") {
    res.statusCode = 200;
    res.setHeader("Content-Type", "application/json; charset=utf-8");
    res.end(JSON.stringify({ tools }));
    return;
  }

  res.statusCode = 404;
  res.setHeader("Content-Type", "application/json; charset=utf-8");
  res.end(JSON.stringify({ error: "Not found" }));
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

node server.js

curl http://127.0.0.1:3000/health
curl http://127.0.0.1:3000/api/tools
curl -i http://127.0.0.1:3000/missing

Common beginner mistakes

• Forgetting that the server keeps running until you stop it with Ctrl+C.
• Trying to use the same port in two terminal windows at once.
• Returning JSON without setting a JSON Content-Type header.

Try changing this next

• Add a `/` route that returns `Welcome to Lumio`.
• Change the server port with `PORT=4000 node server.js`.
• Add one more tool to the `tools` array and call `/api/tools` again.