Hi,
interesting project , you should make the server and clients for VoIP and instant messaging secure and reliable , to underst. from several layers ( points of view ). Today we have a lot of open source.
try out
http://www.linphone.org/
http://www.voip-info.org/wiki/view/O...+VOIP+Software
http://en.wikipedia.org/wiki/Compari..._VoIP_software

I had an idea to make something close private server and client + protocol modification , but it is long job + budget + need to relocate to work in comfort place.

Kindest Regards,

[email protected]