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Clients and Servers

The Internet operates on a simple yet powerful concept: clients and servers. Every time you browse a website, watch a video, or send an email, your device (the client) communicates with another system (the server) that provides the requested data or service.

The Core Idea​

Think of the Internet as a giant conversation. Your computer, phone, or browser asks questions and servers reply with answers.

In this model:

  • The client initiates communication.
  • The server listens, processes, and responds.

What Is a Client?​

A client is any device or software that requests resources or services from a server.

Common examples:

  • Web browsers (like Chrome, Firefox, Edge)
  • Mobile apps
  • Command-line tools (like curl or wget)

Clients don’t store the data permanently, they only display or use it temporarily.

What Is a Server?​

A server is a system (computer or application) that stores, manages, and serves data to clients over a network. It runs specialized software like:

  • Web servers (e.g., Apache, Nginx)
  • Database servers (e.g., MySQL, MongoDB)
  • Mail servers (e.g., Postfix)

Servers are designed for reliability and availability, often running 24/7 in data centers.

How Clients and Servers Communicate​

Communication follows a request-response model, using protocols such as HTTP or HTTPS.

  1. The client sends a request to a server.
  2. The server processes the request.
  3. The server sends a response (like an HTML page or JSON data).

Here’s a simplified example:

GET /home HTTP/1.1
Host: codeharborhub.github.io

The server replies:

HTTP/1.1 200 OK
Content-Type: text/html

<html>
  <body>Welcome to CodeHarborHub!</body>
</html>

Real-World Example​

When you visit https://codeharborhub.github.io:

  • Your browser (the client) sends a request.
  • GitHub Pages (the server) finds and returns the website files.
  • The browser displays them on your screen.

You never directly see the server, but every webpage you view comes from one.

Types of Client–Server Architecture​

TypeDescriptionExample
1-TierClient and server on the same machineLocal software like MS Word
2-TierDirect client-server communicationWeb browser ↔ Web server
3-TierIncludes a database layerBrowser ↔ App server ↔ Database
N-TierDistributed services and APIsModern cloud-based systems

Security & HTTPS​

When data travels between client and server, security is essential. With HTTPS, information is encrypted using SSL/TLS, preventing eavesdropping and tampering.

Key Takeaways​

  • Clients request data or services.
  • Servers store and deliver that data.
  • They communicate through standard protocols (HTTP, HTTPS, FTP, etc.).
  • The request–response model is at the heart of how the Internet works.
  • Modern systems often involve multiple servers and APIs behind the scenes.

“Every click, every page, every message you send, is just one client talking to one server somewhere in the world.”