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by Steve Burnett
You’ve heard that all kinds of information is available on the Internet. It’s true. You’ll find everything from the latest weather satellite photo to software, statistics, and online shopping.
This chapter discusses the services you can use to get to information on the Internet. You might use the World Wide Web, FTP, gopher, telnet, WAIS, or archie. Most likely you’ll use some combination. This chapter goes through each major service and shows you some basic information on how to use that service. Because the Web provides such an easy way to access information on the Internet, and because many of the other services can be used from your Web browser, this chapter concentrates on how to use these services from a Web browser.
The Internet is a completely distributed network, which means that your computer is connected directly not only with the computer down the hallway, but with thousands of others all over the world. Your computer connects to another computer, which is connected to other computers, and so on.
To make matters more complex, the Internet is international in scope. Virtually every country in the world has some form of access to the Internet. For years, there were many services to get to information (FTP, gopher, and so on), but none were easy to use. You had to have all the appropriate software. Then you had to know what service to use and when. And so on. Something like the World Wide Web was needed as a form of “information navigator” to make it easier for users to get to information on the Internet.
The Web began as a network and hypertext project at CERN, a European physics research lab, in 1989. Researchers saw a need for people from any location to be able to share and exchange information and documents in real time from any type of computer. They also wanted a simple and consistent way to handle this information. From this, the Web was born.
The Web uses a set of hypertext links that allow users to easily navigate between documents, graphics, files, audio clips, and so on from sites anywhere on the Internet. When you select a hypertext link in a document, whatever item the link points to is automatically retrieved. One link at a time, Internet users quickly find their way to the various bits of information they want.
The Web is based on a client/server model. The client software package (Web browser software on your computer) contacts a server computer (Web server software) and exchanges messages with that computer through a set of rules that both client and server understand. This set of rules is known as a protocol. Web servers and clients communicate through a protocol known as the Hypertext Transfer Protocol (HTTP). When a Web client program retrieves a document from a Web server, the programs are probably communicating by using HTTP. As you’ll see later in this chapter, other Internet protocols also may be supported by the Web server.
| Of Clients and Servers
The client/server relationship is an important concept in networking, and especially in navigation of the Web. A server is a computer that offers services for other computers to use. Services can be any kind of program, routine, or data provided by the server. For example, a server might return information from a database to which you don’t have direct access. A client is a computer that uses services from a server. The client contacts the server and requests some sort of service. Many times, a client computer uses special software designed to interact with a specially designed server program on the server computer. Under this client/server model, people with different computers in different locations can access information on the same server. You can set up different server computers with different types of data. Because people are using a client software program to communicate with the server, you can develop a different client program for each computer platform that they use. That way, people using Windows or a Macintosh can use client software to access information on a UNIX or Linux server just as easily as UNIX or Linux users can. |
To access the Web, you need client software known as a Web browser. A Web browser is a program that understands how to communicate to a Web server via the HTTP protocol, displays information, and provides a way to represent hypertext links. Many browsers are available. Now, the most commonly used browsers are Netscape’s Navigator and Microsoft’s Internet Explorer. You can get a browser in any number of ways: from your Internet Service Provider (ISP), by buying it in store, by downloading it off the Internet, and so on. After you install the browser and configure the software with your Internet access information, you’re ready to go.
You get information on the Web by using a descriptive address known as a uniform resource locator (URL, pronounced “earl”). Think of an URL as a pointer to an object on the Internet that tells you not only where the object is located, but also what it’s named and how to access it. Everything you access through the Web has an URL.
The syntax of URLs may look intimidating but is really quite straightforward. Here’s an example:
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