Question : Problem: ultravnc failed to connect to server

I have just download and installed ULTRAvnc on my computer and a partner's computer. Mine is XP, his is Vista. We've pretty much left all default config settings. He is on a DSL cable modem, no router. I have a router on my DSL modem. I've determined his IP address by having him access a website where I can see the access log. He runs the server, I try to connect via the view.

I have verified that our respective firewalls permit this program and permit ports 5800 and 5900. Even so, I've tried shutting off the firewall on both ends. I've configure my route to forward port 5900 to my IP.

I get Failed to connect to server. Can any one give me a clue?

Answer : Problem: ultravnc failed to connect to server

What does his IP start with 192.x.x.x 10.x.x.x 172.x.x.x?  A lot of ISPs are NATing their customers due to the cost and lack of need to have public IP addresses.  

Also, it is very unwise to have a PC on the internet (even NATed by the ISP) without a firewall (software or hardware, while I recommend hardware).

I would recommend hamachi, it is a free tool that you can install on both PC's create a secure connection between the two pc's (or more if you like) and then you can allow the ultraVNC traffic as you wish over the hamachi connection.  Hamachi does not need ports forwarded in you firewall, its pretty slick in my book.  Keep in mind that there will be some lag, just try it out, I think you'll see it suits your needs.

https://secure.logmein.com/products/hamachi/vpn.asp?lang=en

http://en.wikipedia.org/wiki/Hamachi

So, I would urge your friend to get a hardware firewall urgently

Hope that helps