Ports on PC?

I am trying to gain an understanding of what ports are and how they work. It is my understanding that a port is an address on a machine that protocols such as FTP and TCP/IP access to communicate with servers and clients. Is it possible to write to ports on your own machine? Is there any way to see what ports are listening on a given machine? If anyone knows of someplace on the web or a book that discusses these issues, I would really appreciate a response.

Take a look at http://www.vijaymukhi.com

This is a good source of information, including tutorials, examples etc.

Hi.

I'm lucky because now I'm taking TCP/IP class and alomost done
CScoket program called Bank Cleint and Server.

When we open Brower, OS automatically uses well-known port 80 to
Brower. OS keeps these well-known port like FTP and so on.
If we write the Internet program like CSocket, we must assign
the port manually except well known port, in the code or input it.

Hope for help.
-Masaaki Onishi-