If you want an online server you have to port forward.
http://portforward.com/
did you even read that we were talking about hamachi...
No, they still need to be in the Hamachi network because the software cannot create a direct tunnel between the two computers if they aren't connected, which is also why you both need to have the software installed
i watched another vid and it looks simple, all it is you would do this:
1.create multiplayer server (tick the local server box in settings and even in fact set the server settings)
2.after the server is created type in console "sv = 1" or something like that
3.in console yet again type "loadlevel_flatgrass" or what ever map you want
4.tell your friend to open console
5.copy your hamachi ip
6.tell them to type in there console "conect (hamachi ip)
im pretty sure this is the right way but your right that both pc's need the software so that your friend connects to the network thing you made.but i would like to test this way with out both players having hamachi