WebServers
by Andy Rush

A web server is just a fancy term for a computer, one probably very similar to the one you are using right now. It's called a web server because this particular computer is running a program, some type of web server software. The server part of the name comes from the program's function. It "serves" something, in this case web pages. There are other types of servers. File servers serve files or programs. Database servers serve, you guessed it, databases.

Excuse Me, Garçon?

The obvious analogy is that a server is like a waiter in a restaurant. His job is to take requests (or orders) from customers, and if the restaurant has what the customer wants, it gets delivered by the waiter. If the restaurant doesn't have what the customer wants, then the waiter will return and inform the customer. "I'm sorry, but we don't have that particular item that you requested". Web servers work very much the same way. You request a document by typing in a web address or URL (Uniform Resource Locator) in your web browser. What you are doing is attempting to communicate with a web server.

Let's break down what happens to our request to the web server (and learn a little about the Internet). First of all, remember that web servers are just computers, usually more powerful than what you use. In order to be web servers and make web pages available to the Internet community, they need to be connected to the Internet network. The Internet is the thing behind the World Wide Web.

Number Please?

Now in order for a computer to be connected to the Internet, it needs to have a unique identity. This identity is known as an IP (Internet Protocol) address. IP numbers have a format of XXX.XXX.XXX.XXX, where each set of three numbers is no larger than 255. An example number is 199.111.95.76. Do you recognize that number? You'll see it again soon. An IP address is as unique as a cellular phone's telephone number. Each cell phone has a unique phone number, and each computer must have a unique IP address on the Internet. No two machines can have the same address. If they do, and are both on at the same time, a conflict occurs. That is for machines that have a fixed number, or static IP address. There is also dynamic addressing (DHCP) that assigns an IP address automatically when the machine starts up. The dynamic addressing system also makes sure that the same address isn't given out to another machine.

Now the IP addressing scheme is set up in such a way as to provide lots of unique numbers, but as you already know, numbers aren't as easy to remember as words. Remember our number 199.111.95.76? Would it be easier to remember it as www.mwc.edu? I thought it might. How about the number 207.46.134.222? Would it be easier to remember it as www.microsoft.com? Of course it would. Enter the Domain Name System (DNS).

What Is the Domain Name System?

A Domain Name System (DNS) server is just another computer. It's main job is to keep track of all the possible web servers at a given location or domain. The domain name for Mary Washington College is mwc.edu . Our domain name is registered with the official organization in charge of keeping domain names straight. "Microsoft.com", "Ford.com", "Whitehouse.org", and "mwc.edu" are all registered domain names. Each one of these domains has several computers that function as web servers. Mary Washington College's DNS server converts all the names you type in as URLs into the IP numbers of the web servers. DNS servers are just like phone books. Just as you would look up a name in a phone book and get their telephone number, the DNS server takes the name (the URL you typed in) and translates it to an IP address.

So let's review what we have so far. If I want to request the home page of Mary Washington College, I type in the URL http://www.mwc.edu. A DNS server attempts to resolve www.mwc.edu to a unique number. The DNS server translates it to the IP address 199.111.95.76. Since that machine has a web server running, the computer treats it as a request for a web page. Also, since nothing else followed www.mwc.edu, the default web page for the server gets displayed; the Mary Washington College Home Page.

What About Other Web Pages On These Servers?

As you may have already realized, there is more than just the "home page" or default web page on these servers. There are thousands of web pages on these servers. To view the home page for Mary Washington College, you don't need to type anything more than http://www.mwc.edu . From the home page, if you click on the word Academics, notice how the URL (the web address) changes in the Address (Internet Explorer) field or the Location (Netscape). It should read:

http://www.mwc.edu/academics/default.htm

What actually happens is that you drop down into a sub-directory called academics on the www.mwc.edu web server, and in that sub-directory is a file called default.htm. There might be many sub-directories on a given web server, and even sub-sub-directories. Most files that are web pages end with a period and htm or html (e.g. default.htm or index.html).

You can go back to the page on Making Web Pages to learn how to create your documents and place them in the proper folder for your account. Then you can let the world see your web pages!

Internet & Web

Web Browsers

Creating Web Pages & Sites

HTML Basics

WYSIWYG Web Editing