Context

This room teaches the basics of the Client-Server model.

Most computers worked alone: they stored their own files, ran their own programs, and did not communicate with other computers.

Soon, multiple organizations around the world started with the idea of interconnecting these systems to facilitate information exchange and resource sharing regardless of distance. Hence, the precursors of the "internet" were born. Networks such as ARPANET, CYCLADES, NPL, and NSFNET paved the way for the modern internet.

Starting hypothesis

• Understand the Client-Server model
• Understand the following concepts on a surface level:
  • DNS
  • Client
  • Server
  • Port
  • Protocol
  • Network

Method / Used Tools

Pizza Delivery

Client-Server Analogy

One of the simplest ways to understand how computer systems provide services is through the analogy of a pizza takeaway.

Imagine Alice wants a pizza. She checks Luigi’s menu and tells Bob what she wants. Bob drives to Luigi’s, places the order, waits for it to be prepared, and brings it back home. This simple interaction mirrors how modern computer systems communicate.

In computing terms, Alice represents the user. The browser acts as the client, Luigi’s Pizza represents the server, and the pizza itself represents the requested resource, such as a webpage or a file.

The fundamental principle of the client-server model is that the client always initiates the request. The server does not actively seek clients; it waits passively for incoming requests and responds when one arrives.

Service, Client, Server

Within this analogy, the service corresponds to the pizza takeaway service itself. The client is Alice (with Bob acting as the intermediary who physically carries the request), and the server is Luigi’s Pizza, which prepares and provides the product.

Technically speaking:

• A client (for example, a web browser) sends a request.
• A server processes that request.