HamachiX is a Mac OS X application for casually creating “virtual” private networks connecting random computers. It’s implemented by wrapping some user interface around the no charge variant of the proprietary Hamachi VPN product. The VPN(s) it creates are named. The machines that join that network providing an appropriate password and get IP addresses like 5.85.1.2. At which point they may exchange data packets with each other. Hamaci is clever in that it uses p2p tricks to bust thru firewalls.

A typical application is to create a community of users who share iTunes collections, or printers, or whatever.

I’m using this to create http listeners on machines which sit on the public network that then forward to listeners on my laptop. When ever my laptop manages to get on the network Hamanchi rejoins the appropriate network and the forwards start working again. This allows me to demo things running my laptop to random folks on the network at large. I do the port forwarding with balance (sudo port install balance).

It looked like I could do something similar with tinc and avoid the issues raised by using proprietary software. But, MacPorts doesn’t include tinc and this certainly was easy. There are lots of choices for how to forward the listener, as I am with balance. I’d be curious to hear of how other people do this kind of thing?

Update: This widget is an alternative to HamachiX once you get started. You can do all this on the command line, say on 10.3.9.

Update 2: Some people find that HamachiX goes crazy and consumes vast amounts of memory.  A problem you can work around by using it as a easier way to install things and then use the widget or the command line tool hamachi from there on in.  The command line tool gives you a better model of what’s really going on.
I’m finding it dependable for simple tcp/ip connections; but mDNS is spotty.  The forums are full of complaints about various non-working scenarios and some of those are real v.s. user confusion.  One of the foundation pieces, tuntap, is also known to occationally misbehave on intel macs.