I've been looking for some software similar to Hamachi LogMeIn, because I am running a server out of my home, but am unable to port forward (know how, but can't). However, I haven't seen any software that will work. The server is running Ubuntu 12.04, but some of my clients will be running running OSX or Windows. I'm looking for software that is free, can be run unattended, and is cross platform. Any recommendations?