After using RXTX for a number of different projects, I've come across many annoying discrepancies and issues that can only sensibly be put down to bugs in the library - deadlocks, race hazards, and monitor threads deep in the RXTX library being left open preventing the program from closing (even though all ports I was using have been closed!) Running the latest "unstable" version has helped a bit, but it's still far from where I'd call it reliable, and activity on the project seems rather low at present.
However, searching for free cross-platform alternatives to RXTX doesn't seem to come up with much else.
Is there another library that anyone's tried with more luck? I don't need parallel port support, just serial, and it doesn't necessarily have to be compatible with RXTX or the javax.comm API.
We have moved to java-simple-serial-connector which seems to be very stable and comfortable at the current release 0.9.0. For now, it works on windows and linux systems. We use it for modem interactions.