Joy of Access: Hosts

Each computer on the Internet is a host. Negative Space, for example, is a host computer. So is the Macintosh on my desktop. The Windows computer holding up my printer is not a host. It isn’t directly on the net. It could be, but it’s too much work when I’ve got a Macintosh here as well. Back when I used a modem and the telephone line to connect, my Macintosh was only a host computer during those times when I dialed in to the net. Now that I have a cable modem, my Macintosh is a host computer whenever I turn it on.

Host computers all have names. Each computer on the Internet is given a semi-unique number called an “IP address”. The “IP” stands for “Internet Protocol”. Computers that are meant to be reached by other people on the net generally also have a “hostname” to go along with that number. This means that, instead of having to type “192.215.84.34”, people can type “cerebus.acusd.edu”. As far as the Internet is concerned, they’re the same thing: the Macintosh on my office desktop. But humans find it easier to remember the latter rather than the former. (And, as well, if my Mac’s number ever changes, I can keep the same name attached to the new number, so people don’t have to care what the number is at all.)

Hosts on the net are divided into two kinds: servers and clients. Clients take information, and servers give information. When you get a great piece of info from the net, you’re getting it from a server of some sort. The server is running special computer software to do its serving. Clients get information. Servers give it. We’ll talk about that later. In fact, we’ll spend the rest of the chapters talking about it. Servers and clients are the birds and the bees of the net. And it’s mostly a matter of semantics: all Internet hosts are clients, and most, even your personal computer, are also servers at some time.

A lot like the birds and the bees. Sometimes you’re on top, sometimes you’re on bottom, sometimes you have no idea where you are.