http

The http module is the backbone of Node.js web servers. It lets you create servers without needing external frameworks (like Express). Let’s break it down:

---

📂 1. Importing

const http = require("http");

---

⚡ 2. Creating a Basic Server

const http = require("http");
 
const server = http.createServer((req, res) => {
  res.statusCode = 200; // HTTP status
  res.setHeader("Content-Type", "text/plain");
  res.end("Hello, World!\n");
});
 
server.listen(3000, () => {
  console.log("Server running at http://localhost:3000/");
});

• http.createServer() takes a callback (req, res) that runs on every request.

• req = incoming request object.

• res = response object you use to send back data.

---

🔎 3. Request (req)

req contains info about the client request:

const server = http.createServer((req, res) => {
  console.log(req.method); // GET, POST, etc.
  console.log(req.url);    // e.g. "/about"
  console.log(req.headers); // headers object
 
  res.end("Check the console!");
});

---

📤 4. Response (res)

You control what goes back to the client:

const server = http.createServer((req, res) => {
  res.writeHead(200, { "Content-Type": "text/html" });
  res.write("<h1>Hello from Node.js</h1>");
  res.end(); // must call end() to finish
});

---

🌐 5. Routing Basics

You can create simple routes by checking req.url:

const server = http.createServer((req, res) => {
  if (req.url === "/") {
    res.end("Home Page");
  } else if (req.url === "/about") {
    res.end("About Page");
  } else {
    res.statusCode = 404;
    res.end("Page Not Found");
  }
});

---

📦 6. JSON Response

const server = http.createServer((req, res) => {
  if (req.url === "/api") {
    res.setHeader("Content-Type", "application/json");
    res.end(JSON.stringify({ message: "Hello API" }));
  } else {
    res.end("Hello World");
  }
});

---

⚡ 7. Handling POST Data (Streams)

Request bodies are streams, so you need to collect data:

const server = http.createServer((req, res) => {
  if (req.method === "POST") {
    let body = "";
 
    req.on("data", (chunk) => {
      body += chunk.toString();
    });
 
    req.on("end", () => {
      res.end("Data received: " + body);
    });
  } else {
    res.end("Send a POST request");
  }
});

---

✅ In Short

• http.createServer((req, res) => {...}) → main entry point.

• req → incoming request (method, url, headers, body).

• res → response (status, headers, body).

• Node servers are low-level → frameworks like Express build on this to make routing & middleware easier.

---