🪴 TJ's Notes 1.0

Web Programming Lecture 19

3 min read

Web Programming - Lecture 19 Notes

Date: 2024.09.23

Time: 11:18

Network Layers in Web Programming

Web applications operate across several layers that work together to facilitate communication between users and servers. These layers are divided as follows:

1. Client Layer:

  • This is the front-end layer, responsible for interacting with the user.
  • Components:
    • Web Browser: The traditional browser (e.g., Chrome, Firefox) used to access web applications.
    • App: Desktop or mobile apps that connect to the server for data.
    • Mobile Browser: Mobile-specific browsers that provide web-based access on smaller devices.

2. Server Layer:

  • This is the back-end layer, responsible for handling user requests and delivering data.
  • Components:
    • Web Server: The server that handles HTTP requests, hosts the website, and serves files or responses (e.g., Apache, NGINX).

3. Business Layer:

  • This layer handles the logic and processing of the application.
  • Components:
    • Application Layer: Processes business logic, handles requests, and executes the necessary operations. This could include frameworks such as Node.js, Django, etc.
    • File System: Manages files, directories, and data needed by the application. For example, it could store uploaded files or configuration data.

4. Data Layer:

  • This layer is responsible for managing and storing data.
  • Components:
    • Database: The storage system that holds the application’s data (e.g., MySQL, MongoDB).
    • External System: Any external services or third-party APIs used by the application for additional data or services (e.g., a payment gateway or social media API).

Node.js

Node.js is a powerful, open-source, server-side runtime environment built on Chrome’s V8 JavaScript engine. It is commonly used for building scalable network applications. A significant feature of Node.js is its event-driven, non-blocking I/O model, which makes it lightweight and efficient.

Modules in Node.js

Node.js applications are composed of modules. These modules help in organizing the codebase and enable code reusability.

  • What is a Module?
    A module is a separate unit of code, essentially a file in Node.js that contains related functionality. Modules help in managing dependencies and maintaining a clean code structure.

  • Core Modules in Node.js: Node.js comes with several built-in modules, such as:

    • fs (File System) for file operations.
    • http for creating web servers.
    • path for handling and transforming file paths.
    • os for accessing operating system information.

HTTP Module in Node.js

The http module in Node.js allows the creation of web servers that can listen for and respond to HTTP requests.

  • Creating a Server with http Module: 
    const http = require('http');
 
const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello, World!\n');
});
 
server.listen(3000, () => {
  console.log('Server running at http://localhost:3000/');
});
    • This code creates a basic HTTP server that listens on port 3000.
    • When accessed, it returns a “Hello, World!” message in plain text.

References

Summary

In this lecture, we covered the structure of web application layers, focusing on how different components interact across the client, server, business, and data layers. We also introduced Node.js as a runtime environment that supports server-side development using JavaScript and explored its module system, particularly focusing on the http module for creating basic servers.

Graph View

Backlinks