closing ports on RH7.2

"2003 AD" <[email protected]> Wed, 1 Oct 2003 22:33:50 -0400 (EDT)
Newsgroups gmane.linux.redhat.release.enigma
Message-ID <[email protected]>
On my Red Hat box:

How can i determine which ports are open? How can i close them.

Thanks

2003AD