Hamachi has to be one of the coolest apps I’ve seen in a while. It lets you establish an externally hosted psuedo VPN server that any number of clients (behind firewalls, mind you) can connect to and share resources.
I came across this while trying to figure out a way to use LAN gaming in Command and Conquer: Red Alert 3 rather than using the online component. I had two computers on my own LAN and one friend across the Internet from me that I wanted to get into the same game. Due to limitations of my network, I couldn’t get both systems on my LAN to connect to the built-in Gamespy online component. That’s when I decided to use a VPN to get my remote friend to dial-in to my system.
Unfortunately, even though the Windows-based VPN allowed my friend through to see my game server, we ultimately could not play. Apparently Red Alert 3, as well as many other games surely, broadcast their packets when in LAN mode rather than route them when in Online mode. Once the game should have started, it kicked my friend out because his routed VPN connection wasn’t providing him with the broadcast packets that a bridged VPN would have provided.
Enter Hamachi. The app itself is an offering from LogMeIn.com and allows users to all join a remote network. It is free for non-commercial use, which made it perfect for our situation. We installed the client on all three machines, connected to the same virtual network, and suddenly we were all playing Red Alert 3 as if we were sitting right next to each other. It was truly a wonderful experience.
The implications of this application go well beyond gaming though. It is basically a bypass around NATed firewalls. You could install it behind your home or corporate firewall to allow remote access to specific clients, or get at their shared files/folders, or maybe connect to your source control server.
There are obviously a slew of security concerns here and I honestly haven’t taken the time to fully investigate them. During install and configuration you are asked if Hamachi should disable Windows services that could be exploited through its VPNish connection. So far I haven’t played with that feature enough to know which services are disabled exactly, but it is probably smart to allow them to be disabled and then make sure your system is still operational and useful for its original purpose.
Enjoy the software, take care regarding security, and please send me feedback if you learn anything interesting!