There's no need to put in any IP address for DS Hobro 0.3 (which can be downloaded from this sites Download/Homebrew/DS App section), you just run the Server.exe on your computer, and then run the app on your DS and connect. Just make sure you've set up your WiFi connection in an official game like Mario Kart, and then try again. It also could be that it's being blocked by a Firewall, or your port666 isn't open.