The jSerial library allows you to open and communicate with other devices through the computer COM ports. It can also be used to communicate with Bluetooth devices over a virtual com port. (jBluetooth library is now available: https://www.b4x.com/android/forum/threads/jbluetooth-library.60184/)...
I think @Erel has updated the file attached to the Integrated B4JPackager11 thread (which I guess is the proper place for it), but not post #102 in the jSerial library thread.
Suggestion to @Erel:
To prevent future confusion, remove the file from your post #102 in the jSerial library thread and add a link to the Integrated B4JPackager11 thread instead.