The Client-Server Model is the Key to Web Design

Each day literally hundreds of millions of people view billions of Web pages on the internet. But how does it work? Where do web pages come from? Where are they stored? How are they stored? And how does a Web Browser know how to find the correct Web page and display it?

This article answers the above questions, by explaining the Client/Server model of web design.

The Client/Server Model

The Client/Server model of web design is very important. All web pages are displayed as a result of cooperative interaction between Web clients and Web servers. Thus, there are two key concepts:

  1. Client. For the purposes of this article, a client is a Web browser. The job of the client (Web browser) is to request Web pages from a server, and display them to a user.
  2. Server. A server is a computer someplace on the World Wide Web that contains one or more Web pages.

What the Web Client (Browser) Does

A Web client, as previously stated, is just an everyday Web browser. Some examples of Web clients are Microsoft Internet Explorer, Mozilla Firefox, Apple Safari, and Google Chromei.

Basically all Web clients do the same thing. They request Web pages from servers, and they display the pages. Most modern browsers are also capable of running “client side” programming languages, like JavaScript, but that is beyond the scope of this article.

What the Web Server Does

A Web server, as previously stated, is a computer located someplace on the World Wide Web, that is able to provide a Web page, upon request. The browser requests a page, and the Web server provides it. Web pages are typically stored as files on the Web server, although sometimes they are produced by “server side” programming languages (for example PHP) but that is beyond the scope of this article.

How Clients and Servers Interact

Based on the definition of a client and the definition of a server, it is not hard to understand how the display of Web pages works, starting from when a user clicks on a link on a Web Page.

Here is what happens:

  1. The user of a web browser (client) clicks on a link.
  2. The link contains the address of a page the user wants the browser (client) to display.
  3. The client then sends a digital message over internet to the server. The message is called an http request. The http request tells the server that the client would like to see the contents of a web page.
  4. Now the server needs to respond to the client request, by sending what is called an http response. Normally, the response will contain the contents of the web page requested by the client

Example

Suppose you click on a link that is supposed to take you to an article posted on the Ezinearticles site.

What happens? According to the explanation of the Client/Server Model given above, the following happens:

  1. First you click on the link for the article on the ezinearticles site.
  2. The client (your browser!) reads the contents of this link and, based on the contents of the link, knows the address of the server that contains the web page you want to see. In this case, the server address is the location of the ezinearticles site, and the page that the server needs to return is the actual page of the article you want to read.
  3. Your browser sends an http request to the EzineArticles server.
  4. The server checks to see if the the article page exists (it should!); and returns the contents of the article page to your browser in an http response message.

Summary

Web browsers and Web servers work together as a client/server team to deliver content on the World Wide Web. Users are more familiar with browsers than servers, but both are essential to delivering billions of pages of content every day.