Computer Systems: A Programmer's Perspective (Global Edition): The Client-Server Programming Model

The Client-Server Programming Model is the foundational architecture for distributed applications. It is not defined by hardware, but by a logical transaction between two processes: a client that initiates a request for a resource, and a server that manages and provides it.

1. The 4-Step Transaction

Every interaction follows a rigid sequence: (1) The client sends a request; (2) The server interprets and manipulates local resources; (3) The server sends a response; (4) The client manipulates the received data (e.g., rendering HTML).

2. Hardware Organization

Communication relies on the Network Adapter, an I/O device. Data travels from the CPU through the I/O Bridge and System Bus to Main Memory. In a web request like http://www.google.com:80, packets traverse these buses to reach the application code.

3. Protocol Abstraction

Modern applications use Network Byte Order (big-endian) for consistency. Functions like getaddrinfo provide Domain name to IP address mapping while remaining protocol-independent.

TERMINAL bash — 80x24

> Ready. Click "Run" to execute.

QUESTION 1

What if different networks have different maximum frame sizes (MTUs)?

The packet is discarded by the first router.

Routers and IP software handle fragmentation and reassembly.

The sender must manually resend smaller frames.

The network automatically increases its MTU.

QUESTION 2

Can a single physical host run both a client process and a server process simultaneously?

No, it causes a hardware conflict on the I/O Bus.

Yes, network applications are process-level interactions.

Only if it has two separate Network Adapters.

Only if one uses IPv4 and the other uses IPv6.

QUESTION 3

In the 4-step transaction, what is the server's immediate action after receiving a request?

Render the HTML content.

Send an acknowledgement to the router.

Interpret the request and manipulate resources.

Terminate the connection to save bandwidth.

QUESTION 4

Which hardware component bridges the Network Adapter to the CPU and Main Memory?

The ALU

The I/O Bridge

The Register File

The USB Controller

QUESTION 5

What is the standard byte order for data transmitted over the Internet?

Little-endian

Network byte order (big-endian)

Host-native order

Bi-endian

Case Study: The 'hostname' Transaction

Analyzing a system command through the Client-Server lens.

A student runs the command linux> hostname on a terminal. This simple utility follows the client-server model to retrieve the machine's name from the operating system.

1. Identify the 'Client Process' and 'Server Process' in this local scenario.

Solution:
The terminal/command process acts as the client requesting the resource. The Operating System kernel acts as the server, managing the system's identity resource.

2. Trace the data path when the server returns the 'hostname' string from memory to the display.

Solution:
The data moves from Main Memory through the I/O Bridge, across the I/O Bus to the Graphics Adapter for display on the screen.

3. If this were a remote request via a web browser, what 'well-known service name' and port would likely be involved?

Solution:
A web browser request typically uses the http service name on port 80.