NoCat Opens all ports

Hello.

I have Nocat installed and is working. The only problem I am 
experiencing is that I have a firewall script that blocks all the ports 
except for web, mail, ftp, ssl, and ssh. I noticed that when nocat runs 
it opens up all the ports and as a result I have all the users in the 
lan connected to a lot of p2p programs and the network gets slugish.

How can I run nocat along with my script so that I don't experience that.

Thanks in advanced.