I have been banging my head for a while now, trying to get a simple server up, that I could host multiplayer games. I could not get around my router, tried opening my port, tried forwarding my ports but to no avail. I thought about getting a dedicated server to work as a facilitator for the NAT punch through... but that is so expensive (100 USD per month seemed too much for mucking about). Then I remembered about Hamachi, which solves the problem of connecting from behind a router. I didnt think that you could actually "connect" to the "Hamachi IP address", but turns out you can.
from the wiki
Hamachi is a zero-configuration virtual private network (VPN) shareware application capable of establishing direct links between computers that are behind NAT firewalls without requiring reconfiguration (in most cases); in other words, it establishes a connection over the Internet that very closely emulates the connection that would exist if the computers were connected over a local area network. C