Yes, I'm running linux (Debian Sarge) and I don't know of anything on the system that could signal to my process.

Somebody suggested that the kernel could have SIGKILLed me if I ran out of memory but I don't really beleive this is the case for the server has plenty of memory and if my program had a memory leak I should have found it before (the other server has less memory, more load and a longer uptime).

Moreover, AFAIK on a SIGKILL Net::Server should write in syslog that it is shutting down, and it didn't.