NotSupported error from Bluez

joselsegura commented 1 month ago

bleak version: 0.21.1
Python version: 3.11.8
Operating System: Debian GNU/Linux
BlueZ version (bluetoothctl -v) in case of Linux: 5.71

Description

I'm trying to subscribe to events for a given characteristic using start_notify, but I'm getting the following error:

bleak.exc.BleakDBusError: [org.bluez.Error.NotSupported] Operation is not supported

I wonder if the problem is my bluetooth USB dongle or if I'm missing some step before trying to call start_notify

What I Did

When connecting a BleakClient to the device and getting the characteristic, I try to start the notifying adding just a lambda function to check if the notifications are received.

Instead, an exception is raised as states above.

async with BleakClient(device, services=[SERVICE_UUID]) as client:
    services = client.services
    characteristic1 = services.get_characteristic(CHARACTERISTIC1_UUID)
    await client.start_notify(characteristic1, callback=lambda *args, **kwargs: print("Notifiation"))
    print("Subscribed to notifications")
    await asyncio.sleep(20.0)
    await client.stop_notify(characteristic1)

Logs

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/joseluis/saj_h1_modbus_exporter/saj_h1_modbus_exporter/retriever.py", line 59, in tool_cli
    asyncio.run(connect_to_device(address))
  File "/usr/lib/python3.11/asyncio/runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/base_events.py", line 654, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/joseluis/saj_h1_modbus_exporter/saj_h1_modbus_exporter/retriever.py", line 30, in connect_to_device
    await client.start_notify(characteristic1, callback=lambda *args, **kwargs: print("Noticiation"))
  File "/home/joseluis/saj_h1_modbus_exporter/venv/lib/python3.11/site-packages/bleak/__init__.py", line 834, in start_notify
    await self._backend.start_notify(characteristic, wrapped_callback, **kwargs)
  File "/home/joseluis/saj_h1_modbus_exporter/venv/lib/python3.11/site-packages/bleak/backends/bluezdbus/client.py", line 958, in start_notify
    assert_reply(reply)
  File "/home/joseluis/saj_h1_modbus_exporter/venv/lib/python3.11/site-packages/bleak/backends/bluezdbus/utils.py", line 22, in assert_reply
    raise BleakDBusError(reply.error_name, reply.body)
bleak.exc.BleakDBusError: [org.bluez.Error.NotSupported] Operation is not supported

dlech commented 1 month ago

I assume this is being called on a characteristic that doesn't support notifications.

Can you share the output of the service explorer example for this device so we can see what characteristics are available and what their properties are?

joselsegura commented 1 month ago

Oh, my...

I just find out that I used the wrong UUID all the time! In my defense, I need to use 2 different characteristics and I switched both UUIDs.

Sorry for the noise

hbldh / bleak