The Client/Server Model

The Client/Server Model is a distributed application structure that divides tasks or workloads between providers (servers) and requestors (clients). A client does not share any of its resources, but requests a server's content or service function. lients therefore initiate communication sessions with servers which await incoming requests.

Examples of computer applications that use the client–server model are Email, network printing, and the World Wide Web. While both the client and server porgrams can reside on the same computer, typically they run on different computers. It's common for a server to handle requests from multiple clients.

The Client/Server Model

How to distinguish the two

Web Client

• Connected to the Internet when needed
• Usually runs web browser(client) software such as Internet Explorer or Firefox
• Uses HTTP
• Requests web pages from a server
• Receives web pages and files from a server

Web Server

• Continually connected to the Internet
• Runs web server software (such as Apache or Internet Information Server)
• Uses HTTP
• Receives a request for the web page
• Responds to the request and transmits the status code, web page, and associated files

The Client/Server Model

Multipurpose Internet Mail Extensions

Clients and servers often need to indicate the type of file being transferred so they know how to handle them. MIME is a standard that helps to classify the types of files used on the internet.

• Originally intended to extend the original e-mail protocol but is also used by HTTP.
• Provides for the exchange of seven different media types: audio, video, image, application, message, multipart, and text.
• Uses subtypes separated by a forward slash(/) to further describe the data.
• Examples: text/css, image/gif, image/jpeg, audio/mpeg, multipart/form-data

The Client/Server Model

A web server determines the MIME type of a file before the file is transmitted to the web browser. The MIME is sent along with the document. The web browser uses the MIME type to determine how to display the document.

How does information get transferred from the web server to the web browser? Clients (such as web browsers) and servers exchange information through the use og communication protocols such as HTTP, TCP, and IP.