The Bellow Link will help you to Forward the Port in any Router...
Step 01: Check the Router Manufacturer and Model No
Step 02: Open the below link (It will show lot of Routers)
Step 03: Find your router on the page and press the link, it will redirect to another page, in that page check the UltraVNC, and press the link, and again it will redirct to another page
Step 04: Follow the steps which is shown in that page to Forward the 5900 port for UltraVNC..