Datasheet

Minasi c01.tex V3 - 05/29/2008 9:45pm Page 4
4 CHAPTER 1 WHY NETWORK?
The Client Piece: A Web Browser
I’ve said that first you’ll need a computer, of course, one that’s running a Web browser program
such as Firefox or Internet Explorer. But let me rephrase that in basic network client-server terms.
There is technically no such thing as ‘‘the World Wide Web.’’ Instead, there is an agreement
about how to transfer text, pictures, and the like, and that agreement is called the HyperText
Transfer Protocol — which is normally shortened to HTTP. The phrase World Wide Web just
refers collectively to all of the HTTP servers on the Internet. When you think you’re surfing a Web
page, what really happens is this:
1. Your client computer asks the Web server (oops, I meant the HTTP server) something like,
‘‘Do you have any documents?’’
2. The Web server responds by saying, ‘‘Here’s my default document,’’ a simple text file that
is the so-called home page for that Web server. The Web server sends that file to your client
using the HTTP protocol.
3. Once your client receives the text file, it notices that the page is full of references to other
files. For example, if the home page that you requested has pictures on it, your Web browser
(HTTP client) didn’t originally know to ask for them, so the Web server (HTTP server)
didn’t send them. Your client notices the lack of the images and requests that the server
send them, which it does — again using HTTP.
Here, ‘‘HTTP client’’ just means a program that knows how to speak a language that transfers
a particular kind of data — Web data. Your computer is deaf to the Web unless it knows how to
request and receive data via HTTP.
Notice what client means here. It doesn’t refer to you, or even to your computer. Instead, it just
means a program that your computer runs.
The Server Piece: A Web Server
Next, let’s consider what’s sitting on my side of the conversation.
I’ll need a computer running a special piece of software that is designed to listen for your
computer (or anyone else’s, for that matter) requesting to see my Web pages via HTTP and that
can respond to those requests by transferring those pages to the requesting client software. You
might call such a piece of software an ‘‘HTTP server’’ program, although almost no one calls it
by that name. You’d more commonly call it ‘‘Web server’’ software. There is a variety of Web
server software that I might run on my Windows Server 2008 computer, but I’m most likely to run
the one that comes free with Server 2008, a program called Internet Information Services (IIS) 7.
Alternatively, I might find, download (probably using HTTP!), and install a popular piece of free
Web server software called Apache.
Once again, notice carefully what ‘‘server’’ means here. It does not really refer to the particular
computer hardware that I’ve got stashed in my network room connected to the Internet. Instead,
server means ‘‘the program running on Mark’s computer that listens for HTTP requests and knows
how to fulfill them.’’
Now that I’ve gone through all of that, consider again the question that I asked at the begin-
ning of the chapter — why are you bothering with a network? The answer is probably because
you want to offer a Web site, either internally or on the public Internet, and you think that IIS is
the best (highest-performance, cheapest, or some combination of the two) Web server software
around — which means that you must use Server 2008, because it’s the only operating system that
supports IIS 7. (Or you could use an earlier version of Server and an earlier version of IIS, but why
not go with the latest and greatest?)