but your code always sets the datalength value to 16

*facepalm*

Well, that certainly explains why i had some "unexpected features"(tm) during tests. You probably just saved me a weekend of debugging. Thank you very much!

Please don't understand the following as a critisism, just as why i prefer a different coding style: Your version of the code is much more compact, which is nice. But it makes it (in my opinion) much harder to read and comprehend, especially for beginners. That's why i also try to avoid pack()/unpack() and also all those implicit things like $_. More explicit code makes it also easier to port between different programming languages.