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How Does a Web Server Work?

You have probably come to this site to find a company that provides Web servers or Web hosting services. But do you actually know how these hosting machines work? It's a good idea to know a little bit about the product or service you are searching for before you begin your quest.

First, it's important to note that this is a two-sided story. Web servers are responsible for storing and exchanging information with other machines. Because of this, at least two participants are required for each exchange of information: a client, which requests the information, and a server, which stores it. Each side also requires a piece of software to negotiate the exchange of data; in the case of the client, a browser like Netscape or Internet Explorer is used.

On the server side, however, things are not as simple. There is a myriad of software options available, but they all have a similar task: to negotiate data transfers between clients and servers via Hypertext Transfer Protocol, the communications protocol of the Web. What type of server software you are able to run depends on the Operating System chosen for the server. For example, Microsoft Internet Information Server is a popular choice for Windows NT, while many Unix fans choose Apache Web server.
A simple exchange between the client machine and Web server goes like this:

1. The client's browser dissects the URL in to a number of separate parts, including address, path name and protocol.

2. A Domain Name Server (DNS) translates the domain name the user has entered in to its IP address, a numeric combination that represents the site's true address on the Internet (a domain name is merely a "front" to make site addresses easier to remember).

3. The browser now determines which protocol (the language client machines use to communicate with servers) should be used. Examples of protocols include FTP, or File Transfer Protocol, and HTTP, Hypertext Transfer Protocol.

4. The server sends a GET request to the Web server to retrieve the address it has been given. For example, when a user types http://www.example.com/1.jpg, the browser sends a GET 1.jpg command to example.com and waits for a response. The server now responds to the browser's requests. It verifies that the given address exists, finds the necessary files, runs the appropriate scripts, exchanges cookies if necessary, and returns the results back to the browser. If it cannot locate the file, the server sends an error message to the client.

5. The browser translates the data it has been given in to HTML and displays the results to the user.

This process is repeated until the client browser leaves the site.

Aside from its functions listed above, the Web server also has an additional number of responsibilities. Whereas a Web browser simply translates and displays data it is fed, a Web server is responsible for distinguishing between various error and data types. A Web server must, for example, designate the proper code for any sort of internal error and send that back to the browser immediately after it occurs. It also has to distinguish between various elements on a Web page (such as .GIFs, JPEGS and audio files) so that the browser knows which files are saved in which format. Depending on the site's function, a Web server may also have numerous additional tasks to handle, including logging statistics, handling security and encryption, serving images for other sites (for banners, pictures, etc), generating dynamic content, or managing e-commerce functions.

Now that you've had a behind-the-scenes tour of a Web server, you can appreciate all the work that goes in to delivering a single page of content to your computer screen. Use this knowledge to your advantage, and keep it in mind when shopping around for your next host.