It can be frustrating to debug a firewall setup while you're
*behind* that firewall. With some firewall/routers, even 
if you have the firewall's port-forwarding for VNC setup 
correctly, you may not be able to connect a Viewer to your 
Server, using the "real world" external IP address that you 
just (tried to) enable. This will result in the cryptic but
popular "error 10061" if you try it.

Fortunately, there's an easy solution. Just open a web-browser
on your PC that's the VNC Server you want to test, and point
it to http://www.GoToMyVNC.com, and run that scan. If
this scan can detect your VNC Server, then your firewall is
setup correctly.