The Bluetooth Serial Port Profile (SPP) is a commonly used connection method using Bluetooth Classic. I've been trying to implement an SPP server on the Dragonboard with the latest kernel on Debian Stretch (209 build):
$ uname -a
Linux linaro-alip 4.9.0-linaro-lt-qcom #1 SMP PREEMPT Mon Apr 3 08:58:12 UTC 2017 aarch64 GNU/Linux
However when I start the server I get the following in the Bluetooth logs:
= bluetoothd: RFCOMM server failed for SerialPort: socket(STREAM, RFCOMM): Protocol not supported (93)
I am being told on the BlueZ mail list:
That usually means that your kernel is incorrectly configured and lacking RFCOMM support.
I am not easily able to swap back to an older kernel so I haven't tested previous versions. Either way it seems like support of RFCOMM might be useful to support. Is there a reason the kernel doesn't support RFCOMM?