ree webhost such as Geocities), and I want those people to be able to do that using nothing but a browser). In order for that to happen, I need to install a webserver program.The webserver program opens a port on my computer called port 80 (this number can be changed, but this is the default number). Then it listens to incoming connections on that port.When someone starts his Internet browser (Netscape, Lynx, Microsoft Explorer etc') and surfs to my website, his browser connects to my computer on port 80 and then sends HTTP commands that my webserver program can understand into it.My webserver program quickly picks up the incoming data and then sends it back into a port that the surfer's browser opened on the surfer's computer. The browser will listen on that port and wait for the data (the HTML page, the picture, the program etc') to come in through it.Note about non-default ports: if you decide to put, say, a webserver on a non-default port, it'll be harder for people to get in. If you decided to put it on port... umm... 8000 instead of 80, people will have to type in your IP address(9) or your hostname(10) if you have one and add a :8000 at the end. For example:142.30.5.79:8080. Simply typing in 142.30.5.79 inside your browser's URL field is as same as typing 142.30.5.79:80, so it's best to put a webserver on port 80 (unless you only want a specific group of people who will be given that number to access your webserver, but such a blockage can be easily cracked using a portscanner(12)).There are different ports for different services(3) so data won't mix up. Imagine your browser getting data your FTP client was supposed to get.I hope you got the main idea of what a port is.Now, there are three kinds of ports: well-known ports, registered ports and dynamic/private ports.The well known ports are those from 0 through 1023. These are default ports for several services. For example: the default port for webservers is 80. Else, how would y...
