[Bluez-devel] Handling simultaneous SCO connections: Does BlueZ have multiple SCO buffers?

George Hansel
2007-07-11T18:30:00Z

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I'm working on a project which is trying to handle multiple SCO
connections and data transfer (from cell phones) simultaneously, whether
that involves using multiple Bluetooth adapters on a single computer
(one SCO connection per adapter) or multiple connections per adapter (up
to the maximum of 3).

I have a process which handles the initial RFCOMM setup, the AT commands
involved in having the computer pretend to be a Hands-Free Device, and
accepts an SCO connection once the phone initiates. It's written in
Python using the PyBlueZ module. Multiple processes are launched in
order to handle multiple connections, and I've so far been able to
establish multiple RFCOMM connections on a single and on multiple
adapters.

The problem arises when I try to start multiple SCO connections (by
pressing buttons on the cell phone, so as to send DTMF tones over the
connection). I am not able to establish multiple simultaneous SCO
connections, and not only that, but the SCO data is directed to a
different process every time the SCO connection resets (due to 3 seconds
of silence - this is a feature of the Hands-Free Profile). This makes it
seem as though there is only one SCO buffer somewhere in the stack, and
any waiting process just reads from it, assuming that it's the proper
data.

My question: Is it true that BlueZ has only one buffer for SCO data? If
this is true, where in the BlueZ stack is this single implementation (in
the kernel drivers? in the bluez-libs? in the bluez-utils?)? I'd have no
reservations about trying to implement a second (or third, as the
protocol truly demands) one. Lastly, if this is not a BlueZ problem at
all, but rather a hardware or PyBlueZ issue, just let me know.

Thanks for any consideration,
George

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