Internet Sharing

Can anyone tell me the name of the Software for sharing dialpad or hottelephone programs through one IP on LAN.

Although, I have tried it with Sygate, Windows NT through Microsoft Proxy Server and Wingate, but these can provide only one-way voice communication across LAN, i.e., user can only listen to the other person on headphone but cann’t send his voice through Mike. All other Voice Chatting programs like Yahoo Voice Chatting, FireTalk work well on these Internet Sharing Programs.