UltraVNC on freebsd

[Antonio Tommasi]

Hi to all,
i've this scenario:

one machine in a private network
one machine with a public machine

i need to control with vnc the machine with private ip by the machine 
with public ip.

This is possibile installing ultravnc on the private machine (with 
freebsd) so i can start the communication with public machine and 
control the private machine? Which VNC?

thanks in advance