chat between 2 remote system

Hi,

I need to write a chat (with more options) between 2 closes systems.
1. basically, I have network A (me) and network B.
2. I can connect to B from A using citrix
3. there is no citrix from A to B.

my questions are:
1. how to a write a program in C++ or C# that use citrix to connect to
the remote system?
2. is there a way for A to connect to B?

I am using http server which is accessible only to people on my
network. what can I do so that also the other network (but only this
network) could connect to mine.

Thanks,
Lior