You can block the p2p ports with a firewall or disable the p2p commands into the game.
For example this is my pf rule, just replace the ports by those you are using, and dont forget to replace "em0".
ports = "{12000, 14000, 14001, 14002, 14003, 14004, 14006, 14010, 14011, 14012, 14013, 14014, 14015, 14020, 14021, 14022, 14023, 14024, 14025, 14099, 15000}"
block out log quick on em0 inet proto tcp from any port $ports
Note : the last line of the pf.conf must be empty
You can show logs of attempts by using this command :
tcpdump -n -e -ttt -r /var/log/pflog