How to open bittorrent ports from the command line in Ubuntu

By default, ubuntu is totally locked and will not allow any incoming connections. To fix this use the following command

sudo iptables -A INPUT -p tcp --dport 6881 -j ACCEPT

this is the port that the built in ubuntu bittorrent client uses.If you are using different port you need to enter instead of 6881.

If you want to lockdown your machine use the following command

sudo iptables -A INPUT -p tcp --dport 6881 -j DROP