I've used netty with udp and tcp protocols.
To my surprise it can be used with serial port as well.
Transport used is rxtx, there are a very few positive recommendations for rxtx.
Can netty be used with jssc instead of rxtx?
Should an application developer really care about the underlying implementation (rxtx or jssc)?
Should there be a problem developing in x86 then swapping to ARM?
There is currently no support for jssc, but you could write your own transport implementation using it.