Creating Your First Node.js Server

# CHAPTER 5

Creating Your First Node.js Server #

1. Introduction #

2. Learning Objectives #

• Use the built-in http module to create a server.

• Understand the req (Request) and res (Response) objects.

• Send an HTTP status code and response headers.

• Listen on a specific network port.

3. Beginner-Friendly Explanation #

1. 1. The Building (The Server): You need a physical place to do business.

1. 2. The Speakerbox (The Port): You need a specific frequency where customers can talk to you.

1. 3. The Cashier (The Callback Function): When a customer talks into the speaker (a Request), the cashier figures out what they want, and hands them food (the Response).

In Node.js, we write a few lines of code to create the building, assign the speakerbox to Port 3000, and write a function that hands back data to anyone who visits http://localhost:3000.

4. Step 1: Importing the HTTP Module #

Create a file named server.js and add:

// Import the built-in module
const http = require('http');

5. Step 2: Creating the Server #

• req: The incoming Request (what the user asked for).

• res: The outgoing Response (what we will send back).

const server = http.createServer((req, res) => {
    
    // 1. Tell the browser "Success (200)" and "I am sending you plain text"
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    
    // 2. Send the actual data and end the connection
    res.end('Welcome to my Node.js Server!');
});

6. Step 3: Listening on a Port #

const PORT = 3000;

// Tell the server to listen on door 3000
server.listen(PORT, () => {
    console.log(`Server is running and listening on port ${PORT}`);
});

7. The Complete Code #

const http = require('http');

const server = http.createServer((req, res) => {
    // Basic routing logic
    if (req.url === '/') {
        res.writeHead(200, { 'Content-Type': 'text/plain' });
        res.end('Home Page');
    } else if (req.url === '/api/users') {
        // Returning JSON instead of text
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ name: 'John Doe', role: 'Admin' }));
    } else {
        // 404 Error
        res.writeHead(404, { 'Content-Type': 'text/plain' });
        res.end('404 - Page Not Found');
    }
});

server.listen(3000, () => {
    console.log('Server running on port 3000');
});

To run this: Open your terminal and type node server.js. Then visit http://localhost:3000/api/users in your browser.

8. Backend Workflow: Why Pure Node.js is Painful #

9. Best Practices #

• Never Hardcode Ports: In production, companies like Heroku or AWS assign random ports dynamically. You should always use environment variables. const PORT = process.env.PORT || 3000;. This says: "Use the server's requested port, but if we are on my local laptop, use 3000."

10. Common Mistakes #

• Forgetting res.end(): If you forget to call res.end() inside your server block, the server will accept the request but never finish responding. The user's web browser will show a spinning loading wheel forever until it eventually times out.

11. Exercises #

1. 1. Explain the roles of the req (Request) and res (Response) objects in the http.createServer callback function.

12. Coding Challenges #

• Challenge: Modify the server.js file to add a new route: /about. If a user visits /about, return an HTML string: <h1>About Us</h1>. Make sure to change the Content-Type header to text/html.

13. MCQs with Answers #

14. Interview Questions #

• Q: Explain the purpose of process.env.PORT when defining a server's listening port.

• Q: Why do developers rarely use the raw http module to build large-scale REST APIs? What specific challenges arise?

15. FAQs #

16. Summary #

17. Next Chapter Recommendation #