check out your firewall
it is most likely the problem
here is what i did:
-by default, windows will block the connection
-i dont know how to change the access with windows firewall
-if you have firewall like comodo or zone alarm, turn it on. yes, i say it right, turn it ON. after that, run combat arms, then the firewall by default is going to ask u if u wanna allow the connection to be established or not. if it is working, then the next time you can turn off the firewall for reducing lag
hope it wil help