Slide 1

The Web server

On the opposite side of the communication channel, is the server, which serves the document as requested by the client. A server appears as only a single machine virtually: this is because it may actually be a collection of servers, sharing the load (load balancing) or a complex piece of software interrogating other computers (like cache, a DB server, or e-commerce servers), totally or partially generating the document on demand.

Slide 2

A server is not necessarily a single machine, but several server software instances can be hosted on the same machine. With HTTP/1.1 and the Host header, they may even share the same IP address.

Slide 3

• Client-server architecture is an architecture of a computer network in which many clients (remote processors) request and receive service from a centralized server (host computer).
• Client computers provide an interface to allow a computer user to request services of the server and to display the results the server returns.
• Servers wait for requests to arrive from clients and then respond to them.