I am developing an application that is similar to a Hands-free service
written in python.
From time to time, I encounter an "Address already in use" error when
attempting to bind a socket to a particular local adapter. The python
code looks like:
Listener = BluetoothSocket(SCO)
Listener.bind((addr1, ))
Listener.listen(1)
strace shows this as:
3328 socket(PF_BLUETOOTH, SOCK_SEQPACKET, 2) = 5
3328 bind(5, {sa_family=AF_BLUETOOTH,
sa_data="\xa2\xc7\x07\x83\x15\x00\x13\xad\x76\x2d\xf4\xf2\x42\x09"...}, 8) = 0
3328 listen(5, 1) = 0
Subsequently, in a separate python thread (is this significant?), I issue:
sock, whence = Listener.accept()
strace shows this as:
3343 accept(5, <unfinished ...>
...
3343 accept(5, <unfinished ...>
...
3343 <... accept resumed> {sa_family=AF_BLUETOOTH,
sa_data="\x4e\xe4\xec\xfd\x1d\x00\xb4\x3b\x82\x04\x20\x04\xbb\xb7"...}, [8]) = 10
After many send() and recv() calls on the socket, it is closed.
Sometimes, the accept-recv-send-close cycle is repeated a number of times.
At the conclusion of the program the Listener socket is always closed.
Because, initially, it looked like the problem was related to not
closing this socket, I added logging so that I could be absolutely
sure it had been closed.
Now that you understand what the program does, we can get down to
explaining the problem.
I can run the program muliple times with no error, but occasionally
the
Listener.bind((addr1, ))
raises a Bluetooth error (98, 'Address already in use')
When this happens, I find that there is a file /sys/class/bluetooth/sco
that contains:
A2:C7:07:83:15:00 00:00:00:00:00:00 4
When we don't experience this problem, this file doesn't exist or is empty.
The contents of the file correspond to the bind() call, but I would
expect this to be cleaned-up on a close() of the listener. Usually it
is, but sometimes not. There are no obvious correlations with external
events as far as I can tell.
The problem persists as long as /sys/class/bluetooth/sco is non-empty,
and I have not discovered any way to continue other than to reboot,
which causes the file to disappear.
Any pointers on where to look next would be greatly appreciated.
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