The demo version seems to work fine, however it only lasts for 30 minutes. After installing and restarting, it sets up a server running on port 9000 which allows you to configure it via a web browser by pointing it to http://youripaddress:9000. Best of all, while not free, it's only $20.
[robg adds: I've actually received a similar question via email on a couple of occasions now, so I felt this was worth posting. I haven't tested the app (no Xbox), and there may be other free or inexpensive solutions to do this -- if you know of such, please post them in the comments!]

