[Libreoffice-bugs] [Bug 120663] No impress remote: Impress incompatible with current bluetooth stack on linux (RFCOMM server failed for LibreOffice Impress Remote: rfcomm_bind: Address already in use)

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=120663

--- Comment #12 from felix.huber at schyf.de ---
This issue was annoying me for a while too. So I sat down and debugged bluez to
see why the bind fails: LO is using the default channel (3) for the RFCOMM
protocol as it should be. However, the bind call fails, because another process
has already bound that channel via DBUS. Changing the default RFCOMM channel in
the bluez source temporaliy to 2 (UDP, unused) and recompiling bluez made
remote impress work immediately!

So I inspected the DBUS users via the old mdbus tool from openmoko and it
turned out that the other process is PulseAudio: The HS profile needs the
RFCOMM for the AT Commands and registers channel 3. Stop PA and impress remote
works again.

So now we have two programs that need RFCOMM for the mobile phone. :-(
One solution would be that LO explicitly requests channel 2 instead of the
default one. Channel 2 is UDP and unused to my knowledge. This will work until
another programm needs RFCOMM and chooses 2 as a free channel...

Or, in the long run, there needs to be some kind of multipexing between the
apps that use the RFCOMM protocol.

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