I get this same error using hamachi though.

Sorry for the problems. We're gonna need much more info than that to help you. What factorio version, what operating system. Preferably also a log file .

And just a guess: Is it version 0.10.8 on OSX Yosemite? If it is, then you both will need to download the experimental version 0.11.8, because ...

When my friend launches Factorio it just instantly crashes don't know what to do we just want to play on the multiplayer ;/.