Is there a java library or framework (other than the javax.comm provided by Sun) that is easy to use when accessing serial and parallel ports ( especially RS-232 ).
I need something free that will work both on Windows and Linux.
As andri pointed out RXTX is pretty much your best choice. There is an article on getting started with RXTX on Windows here (relating to RXTX 2.1).
The most common framework used for this is rxtx.
If free isn't necessary -- remember, your time isn't free -- then Serial IO SerialPort might be useful. It's the only thing I found that works as-is on all of the following:
You do get source with the product, albeit with some weird and annoying build practices.
FWIW, I'm just a contented user, not affiliated with the company.
rxtx as the other posters have said. I've been using it and it works nicely. There is a problem if using nonstandard highspeed baudrates (multiples of 115200 e.g. 230400, 921600 are OK, but 1MB is not even if the hardware & underlying OS supports it), I've been told this will be corrected in rxtx 2.2.