Question : Problem: cannot connect to a pc that has ultraVNC server installed

Hello, I have four pc's  in an office1. They all have windows xp pro sp 2 installed and ultraVNC working as a service. They are in the same workgroup and connected to a zyxel router. The router doesn't have firewall. I want to log on  to any of this computers to make helpdesk tasks when needed , because the office1 is in a different location from when I usually am. If I'm at the office1 I can connect my laptop  to all of them , but if I'm in other location ,  when I try to connect using the ultraVNC viewer , I always get  the message "Failed to connect to server"!. I've forwarded  the ports 5900, 5901, ....5800, 5801, one for each computer ip and, I am using  dyndns service since my router has a dynamic ip . I've also can connect to the router remotely. I've checked some manuals and everything appears to be ok . Any idea about what can be wrong? Thanks in advance.

Answer : Problem: cannot connect to a pc that has ultraVNC server installed

At the end  the problem was that the firmware configuration of the router was wrong, so I wrote to zyxel and they sent me a new firmare. I've installed the firmware, reconfigured the router and opened the ports, and this time it worked properly.