Monitoring traffic on ports..
 

I was just wondering, is there a command in linux that would show me how many MB's have been transferred to and from a certain port? Preferably on a monthly basis.

heh start logging traffic and write a perl script

Ok, considering that having asked a question like that, it would be a reasonable guess that

1. I have no clue how to log traffic
2. I can't program in perl

Now can someone give me a useful answer?

iptables -L -v will tell you how many packets and the bytes that where transfered. but you have to have a rule in place first. Example of tracking all tcp traffic coming in on port 80.

iptables -A INPUT -i eth0 --dport 80 -j ACCEPT

you can try iptraf