Before you venture out onto the Internet using the information in this chapter, you should become familiar with some concepts and terminology.
A server is a computer that stores files and "serves" them whenever requested. For example, you might think of a Web server as a big storehouse for .html files. Its job is to store .html files, wait for another computer to request files, and then find the requested files and "serve" them to the requesting computer. And, yes, your Unix system might be a Web server, but it doesn't have to be.
A client is a program that runs on your Unix system and is used to access data on a server. For example, your lynx Web browser is a clientthat is, it runs on your Unix system and is used to access files on a Web server.
An IP (Internet Protocol) address is the address of a specific computer. This address identifies a computer, much the way your street address identifies your home. You use IP addresses, for example, every time you access a Web page. You may type in www.raycomm.com (which is called the host name), but behind the scenes, that's translated into a specific IP address, such as 192.168.141.12. You will use host names (such as www.ibm.com or www.sun.com) more often, because they're easier to remember than a string of numbers. Whether you type in a character address or a number address, all you're doing is accessing a specific address for a specific computer.
Protocols are the languages that computers use to communicate with one another. For example, FTP (File Transfer Protocol) is used to transfer files from one computer to another. HTTP (Hypertext Transfer Protocol) is used to transfer data on the World Wide Web.
Ports are like a computer's earsthey're "places" that computers listen for connections. Most Web servers run at port 80, and if you connect to http://www.raycomm.com:80/, you're explicitly saying that you want to talk to the www.raycomm.com computer, at port 80, using HTTP. You could specify a different protocol (FTP, for example) or a different port (8080, for example) to communicate with the same computer in a different way, as Table 12.1 shows.