Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.
One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.
http://social.msdn.microsoft.com/Forums/en-US/vsto/thread/b55b368f-82e5-42e6-af9e-b056a0fe3ad0