It is not an issue, but more a feature request:
If you start USBtin viewer and want to select the right COM port, all (virtual) ports are listed.
If you have other devices connected at USB ports e.g. FTDI/Silabs USB/UART devices, they are also listed in the COM port dropdown menue.
Then you maybe connect with the wrong device.
Therefore it would be better if only the USBtin devices are listed in the COM port menue.
It can be accomplished by filtering out the USB serial port devices by USB VendorID.
I recently did this in python and it worked, so it should be possible in Java, too.