POSIX message queues? I don't know of any existing Java interface to this... I did find the jmqueues project on Java.net, but it doesn't look like anything is even there... If you need 2 Java programs to talk to one another, it would probably be a better idea to go with RMI. If you need to interface with an existing program that already uses POSIX message queues for IPC - you'd probably have to use JNI to wrap the POSIX libraries.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.