Introduction
Node.js, an event-driven JavaScript runtime, has revolutionized how developers build server-side applications. At the heart of many web applications is an HTTP server that listens to incoming client requests, processes them, and sends back responses. While building a complex web application often requires frameworks like Express, setting up a basic HTTP server from scratch using Node.js can be an excellent way to understand the inner workings of web servers.
In this post, we will walk through the process of creating a simple HTTP server using the built-in http module in Node.js. By the end of this guide, you will have a fundamental understanding of how to handle incoming requests, send back responses, and manage routes. This knowledge will be crucial as you move toward more advanced topics, such as creating APIs or building complex web applications.
What is the http Module in Node.js?
The http module in Node.js allows you to create an HTTP server, which is capable of handling HTTP requests from clients (typically web browsers or other web services) and sending responses back. This module is built into Node.js, meaning you don’t have to install any external libraries to use it.
Key Features of the http Module:
- Create a Web Server: It allows you to create an HTTP server that listens for incoming requests.
- Handle Requests and Responses: You can write handlers for different types of HTTP requests (like GET, POST, etc.).
- Serve Data: Send HTML, JSON, or other types of data as responses.
- Manage Routing: Implement basic routing logic based on the request URL.
While building a more complex application may require additional libraries or frameworks, understanding the http module provides the foundation for any web development in Node.js.
Setting Up Your Project
Before we dive into the code, let’s make sure we have a working Node.js environment and an initialized project.
1. Install Node.js
To follow along with the examples in this post, you need to have Node.js installed. You can download it from Node.js’s official website. Once installed, you can check the version using:
node -v
2. Initialize a New Node.js Project
Once Node.js is installed, initialize a new project directory where we will create our HTTP server.
- Create a new directory:
mkdir my-http-server
cd my-http-server
- Initialize a new
package.jsonfile:
npm init -y
This creates a package.json file with default settings.
Creating Your First HTTP Server
Now, let’s create a simple HTTP server. We will use the http module to set up the server, define the request handler, and specify the response.
1. Import the http Module
In Node.js, to work with HTTP requests, we need to import the built-in http module.
const http = require('http');
2. Create the Server
Next, we create an HTTP server using the http.createServer() method. This method takes a callback function that will handle incoming requests.
const server = http.createServer((req, res) => {
res.statusCode = 200; // HTTP status code for successful requests
res.setHeader('Content-Type', 'text/plain'); // Define the response content type
res.end('Hello, World!'); // Send the response body
});
In the callback function:
req: Represents the incoming request from the client.res: Represents the response we will send back to the client.
We set the status code to 200 (indicating that the request was successful) and the content type to text/plain (plain text).
3. Start the Server
After creating the server, we need to specify the port and start the server to listen for incoming requests. We use server.listen() to bind the server to a specific port.
server.listen(3000, () => {
console.log('Server running at http://localhost:3000/');
});
This tells the server to listen on port 3000 and logs a message once the server is successfully running.
4. Complete Code Example
Here’s the full code for setting up a basic HTTP server in Node.js:
const http = require('http');
// Create the HTTP server
const server = http.createServer((req, res) => {
// Set the response status code and headers
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
// Send the response body
res.end('Hello, World!');
});
// Start the server and listen on port 3000
server.listen(3000, () => {
console.log('Server running at http://localhost:3000/');
});
5. Running the Server
Save this code in a file called server.js, and run it using Node.js:
node server.js
You should see the message:
Server running at http://localhost:3000/
Now, open a browser and navigate to http://localhost:3000. You should see the message “Hello, World!” displayed in the browser.
Handling HTTP Requests
1. Understanding the Request Object
The req (request) object contains information about the incoming request. Some important properties of req include:
req.method: The HTTP method (e.g., GET, POST, PUT, DELETE).req.url: The URL of the incoming request.req.headers: The headers of the incoming request.req.body: The body of the incoming request (if applicable).
2. Different HTTP Methods
Web applications often handle different HTTP methods for different types of actions. For example, a GET request might be used to fetch data, while a POST request could be used to submit data.
We can check the request method and handle it accordingly. Here’s an example of handling different HTTP methods in the server:
const http = require('http');
const server = http.createServer((req, res) => {
if (req.method === 'GET') {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('GET request received');
} else if (req.method === 'POST') {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('POST request received');
} else {
res.statusCode = 405; // Method Not Allowed
res.end('Method Not Allowed');
}
});
server.listen(3000, () => {
console.log('Server running at http://localhost:3000/');
});
This server will respond differently depending on whether the request is a GET or POST request.
3. Parsing URL Parameters
The req.url property gives us the URL of the incoming request. In more complex applications, you may need to parse the URL and handle different routes or extract parameters from the URL.
For instance, if the URL contains dynamic segments (e.g., /user/123), you can extract the ID from the URL and use it to fetch data from a database or perform other operations.
const http = require('http');
const url = require('url');
const server = http.createServer((req, res) => {
const parsedUrl = url.parse(req.url, true); // Parse the URL and query string
const pathname = parsedUrl.pathname; // Extract the path
const query = parsedUrl.query; // Extract the query parameters
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
if (pathname === '/user') {
const userId = query.id;
res.end(User ID: ${userId});
} else {
res.end('Welcome to the server!');
}
});
server.listen(3000, () => {
console.log('Server running at http://localhost:3000/');
});
In this example, if you navigate to http://localhost:3000/user?id=123, the server will extract the id query parameter and return it in the response.
Sending Different Types of Responses
While sending plain text responses is common in simple applications, web servers often need to send different types of content, such as HTML, JSON, or even files.
1. Sending HTML Responses
To send HTML content, you can change the Content-Type header to text/html. You can also use template engines or manually generate HTML in your server code.
const http = require('http');
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/html');
res.end('<h1>Welcome to My Server</h1>');
});
server.listen(3000, () => {
console.log('Server running at http://localhost:3000/');
});
2. Sending JSON Responses
When building APIs, you often need to send JSON responses. You can set the Content-Type header to application/json and use JSON.stringify() to send JSON data.
const http = require('http');
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'application/json');
const responseData = { message: 'Hello, World!' };
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