[HELP] multiplayer gaming over internet on a pc connected to LAN

[pramudit]

i have got a 3G modem and galaxy Y. when i connect via modem, it connects as dial up so my friends are able to easily connect to my game via my IP address. But when i use my Galaxy Y, it tethers connection and my computer is connected as a node in LAN and my friends are not able to connect to my game via my IP address. What i need to do so that my friends can connect to my Game when i am connected via SGY?????

(please dont suggest to use garena or gameranger)