iptables centos 5

Hello,

My linode works fine with Centos 5.5, two IPs (one for Apache and one for Nginx). ports 80and 21 are obviously open.

Now, I am struggling to open port 30000.

What puzzles me is that

iptables -L

returns

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

It looks like my current rules are somewhere else and that would explain why adding rules for port 30000 does not work. But I don't really understand what's going on here.

Where are the rules for ports 80 declared?

How could I add rles so that I can run bidirectionnal socket on that port.

(I need that 30000 port to communicate with Canada Post's shipping module

Thanks!