I am new to linux, and I have begun to try to understand some of its basics. I have two questions. Do I need the following ports open to simply surf the net, do email, and download the occasional program?

Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
Interesting ports on localhost.localdomain (127.0.0.1):
(The 1596 ports scanned but not shown below are in state: closed)
Port State Service
25/tcp open smtp
111/tcp open sunrpc
631/tcp open ipp
6000/tcp open X11
10000/tcp open snet-sensor-mgmt

Nmap run completed -- 1 IP address (1 host up) scanned in 1 second

I have tried to configure my firewall using ipchains, and would like to test it. Is there any way that I can do this? I even searched google and AO, and was only successful in finding windoz based scans. (Note: An online scan is probably not possible in my situation because I am behind a router.) Thanks, sorry if this is kind of long and rambling.