Testing Rails applications built on an Ubuntu guest

[xtheunknown]

codecore.ca/how-to-test-the-rails-app-running-on-your-computer-on-mobile-devices-like-an-ipad-or-iphone/ implies that I just view Network -> Connection Information on 13.04 and type in the IP address into my phone's browser. I get "Web page not available", even though localhost:3000 in Firefox (in Ubuntu) works. How do I get things working? The host is Windows 7 Home Premium.