Skype uses a different type of communication protocol, it's down to how it communicates which makes or breaks this whole thing...
It's like with FTP there's 2 modes, Active and Passive... Active pretty much always works, but Passive might not work if you are behind a router... i cannot explain why... nor do i know how exactly the LiNK communication protocol is designed... but, yes... i do know that it don't work by experience, not personal experience but... i was in the original LiNK testing, during which time we tested this and all kinds of other stuff...