Exclusive serial port access on OSX

Question

I'm working on an open source program that uses gnu.io (RXTX) to talk to a microcontroller over a USB serial port. The app runs on Windows, Linux and OSX. It relies on gnu.io for portable serial port access. One Macbook user has posted a log showing evidence of two things:

• While the application has the serial port open something causes RTS to pulse, resetting the microcontroller.
• While the application has the serial port open something changes the baudrate temporarily, causing garbage to appear on the input. (Normally this microcontroller/firmware/USB combination is not susceptible to "line noise" style garbage characteristic of bad baud rates).
• This happens periodically while the application sits idle (reacting/logging when spontaneous messages arrive after the RTS induced reset)

I suspect that some other program is opening the same serial port occasionally (eg searching for a connected device). How do I prevent that on OSX?

Answer 1

as far as I know, RXTX does not allow anyone else to use a Serial port it's using, and throws an exception if the port is already in use when it tries to open it. sounds like a RXTX bug to me