I wouldn't want to run a VNC server on a public network without encryption. If you send the password to start a VNC session it's sent unencrypted. I.e. easy for people who know stuff about it to sniff it out and take over your computer......
However routing a specific port to a certain computer behind the router should be easy, should be in the router's manual.
VNC uses a standard port number of 5901 or thereabouts, isn't it?
