Best message-passing library for Java?

I'm toying with writing a network-distributed program in which various peers (instances of the program) communicate to each other by passing various messages. Java seems like the appropriate choice because speed isn't absolutely important (network lag will slow everything down,) and WORE would be very nice. I've found numerous message-passing libraries for Java, but would like to know which one /prog/ likes best.

I'd prefer the library to be FOSS (don't care if GPL/LGPL/BSD/etc.)

>>2

reinvent the wheel