Windows 11 - WinRT backend error [WinError -2147024874] in _get_services

[DaLLuZZ]

Setup:

Windows 11 (22H2 version 2261.4317)
Python 3.12.10

bleak-3.0.1
winrt-Windows.Devices.Bluetooth-3.2.1
winrt-Windows.Devices.Bluetooth.Advertisement-3.2.1
winrt-Windows.Devices.Bluetooth.GenericAttributeProfile-3.2.1
winrt-Windows.Devices.Enumeration-3.2.1
winrt-Windows.Devices.Radios-3.2.1
winrt-Windows.Foundation-3.2.1
winrt-Windows.Foundation.Collections-3.2.1
winrt-Windows.Storage.Streams-3.2.1
winrt-runtime-3.2.1

Minimal python code to reproduce the issue:

import asyncio
import bleak
_client = bleak.BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=("0000ffe5-0000-1000-8000-00805f9b34fb",), timeout=10.0, pair=False,)
asyncio.run(_client.connect())

Console log:

C:\Users\khrusas>python
Python 3.12.10 (tags/v3.12.10:0cc8128, Apr  8 2025, 12:21:36) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> import bleak
>>> _client = bleak.BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=("0000ffe5-0000-1000-8000-00805f9b34fb",), timeout=10.0, pair=False,)
>>> asyncio.run(_client.connect())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 691, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\site-packages\bleak\__init__.py", line 660, in connect
    await self._backend.connect(self._pair_before_connect, **kwargs)
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\site-packages\bleak\backends\winrt\client.py", line 430, in connect
    self.services = await self._get_services(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\site-packages\bleak\backends\winrt\client.py", line 735, in _get_services
    result = await FutureLike(
             ^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\site-packages\bleak\backends\winrt\client.py", line 1195, in __await__
    yield self  # This tells Task to wait for completion.
    ^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\site-packages\bleak\backends\winrt\client.py", line 1136, in result
    raise WinError(error_code)
PermissionError: [WinError -2147024874] The device does not recognize the command.

BUT

If I change the setup to following (Windows 11 -> Windows 10):

Windows 10 (22H2 version 19045.6456)
Python 3.12.10

bleak-3.0.1

And try to connect to the same BLE peripheral device following the same way, everything works fine (no any errors are raised from WinRT backend, so the conection is successfull).

I attached zip-archive which contains all packets captured in Wireshark .pcapng format (captured by Windows BTP btvs.exe):

• win11_error.pcapng (from Windows 11 - error during connection)
• win10_no_error.pcapng (from Windows 10 - successfull connection)

wireshark.zip

[dlech]

Not sure that we can do anything about this one since it is an OS error.

Looking at the packet capture, one thing that jumps out at me is on Windows 10, the "Connection Parameter Update Request" is accepted while on Windows 11, it is rejected. I can't see any difference in the request though, other than the timing. The parameters look the same.

[dlech]

Perhaps WinRT in Windows 11 considers the resulting "Error Response - Attribute not found" response to be critical

I don't think so. This is the standard way of saying "there are no more entries". Every device does this.

[DaLLuZZ]

I just tried to run the same steps on Windows 11 but with another peripheral device from the same vendor, and it successfully connects. I guess it is just older or newer version of the same device, because as I can see from the captured packets it has smaller MTU of 23 bytes and it supports shorter connection intervals.

Windows have accepted connection parameter update request sent by peripheral, there are packets 158 and 159 in the attached pcapng

win11_no_error.zip

[dlech]

Windows 11 did introduce a [RequestPreferredConnectionParameters](https://learn.microsoft.com/en-us/uwp/api/windows.devices.bluetooth.bluetoothledevice.requestpreferredconnectionparameters?view=winrt-26100#windows-devices-bluetooth-bluetoothledevice-requestpreferredconnectionparameters(windows-devices-bluetooth-bluetoothlepreferredconnectionparameters) method.

I've never tried using it before. You could try hacking it into Bleak before the _get_services() call so see if it makes a difference.

[DaLLuZZ]

test.py

import asyncio
import bleak  
print(bleak.__file__)

_client = bleak.BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=("0000ffe5-0000-1000-8000-00805f9b34fb",), timeout=10.0, pair=False,)
asyncio.run(_client.connect())

Changes made to the version 3.0.1 of bleak:

--- a/bleak/backends/winrt/client.py
+++ b/bleak/backends/winrt/client.py
@@ -24,6 +24,7 @@ from winrt.windows.devices.bluetooth import (
     BluetoothCacheMode,
     BluetoothError,
     BluetoothLEDevice,
+    BluetoothLEPreferredConnectionParameters,
 )
 from winrt.windows.devices.bluetooth.genericattributeprofile import (
     GattCharacteristic,
@@ -366,6 +367,18 @@ class BleakClientWinRT(BaseBleakClient):
                 # Instead it has the concept of a GATT session that is owned
                 # by the calling program.
                 self._session.maintain_connection = True
+
+                # HACK: try RequestPreferredConnectionParameters before _get_services
+                print("attempt to call RequestPreferredConnectionParameters method")
+                try:
+                    self._params_request = BluetoothLEDevice.request_preferred_connection_parameters(
+                        self._requester,
+                        BluetoothLEPreferredConnectionParameters.power_optimized, # tried throughput_optimized, balanced and power_optimized
+                    )
+                except Exception:
+                    print("RequestPreferredConnectionParameters not supported")

console log:

C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d>python test.py
C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py
attempt to call RequestPreferredConnectionParameters method
Traceback (most recent call last):
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\test.py", line 6, in <module>
    asyncio.run(_client.connect())
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 691, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py", line 660, in connect
    await self._backend.connect(self._pair_before_connect, **kwargs)
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\backends\winrt\client.py", line 443, in connect
    self.services = await self._get_services(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\backends\winrt\client.py", line 748, in _get_services
    result = await FutureLike(
             ^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\backends\winrt\client.py", line 1208, in __await__
    yield self  # This tells Task to wait for completion.
    ^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\backends\winrt\client.py", line 1149, in result
    raise WinError(error_code)
PermissionError: [WinError -2147024874] The device does not recognize the command.

I tried all 3 possible options for RequestPreferredConnectionParameters: throughput_optimized, balanced and power_optimized, but it never succeeded.

I captured packets for every case (throughput_optimized, balanced and power_optimized), attached in archive

win11_with_reqprefferedconnparams.zip

[DaLLuZZ]

I modified code in winrt/client.py one more time (in some kind of a dumb way to be honest, but it seems that it changed the result of call to _get_services method, so winrt didn't throw the error)

diff:

--- a/bleak/backends/winrt/client.py
+++ b/bleak/backends/winrt/client.py
@@ -18,12 +18,15 @@ from ctypes import WinError  # type: ignore[attr-defined]
 from typing import Any, Generic, Optional, Protocol, Sequence, TypeVar, Union, cast
 from warnings import warn

+import time
+
 from winrt.system import Object
 from winrt.windows.devices.bluetooth import (
     BluetoothAddressType,
     BluetoothCacheMode,
     BluetoothError,
     BluetoothLEDevice,
+    BluetoothLEPreferredConnectionParameters,
 )
 from winrt.windows.devices.bluetooth.genericattributeprofile import (
     GattCharacteristic,
@@ -366,6 +369,22 @@ class BleakClientWinRT(BaseBleakClient):
                 # Instead it has the concept of a GATT session that is owned
                 # by the calling program.
                 self._session.maintain_connection = True
+
+                # HACK: try RequestPreferredConnectionParameters before _get_services
+                print("attempt to call RequestPreferredConnectionParameters method")
+                try:
+                    self._params_request = BluetoothLEDevice.request_preferred_connection_parameters(
+                        self._requester,
+                        BluetoothLEPreferredConnectionParameters.power_optimized, # tried throughput_optimized, balanced and power_optimized
+                    )
+                except Exception:
+                    print("RequestPreferredConnectionParameters not supported")
+                    self._params_request = None
+
+                print("sleep in")
+                time.sleep(10)
+                print("sleep out")
+
                 # This keeps the device connected until we set maintain_connection = False.

                 cache_mode = None

code used for testing this time:

import asyncio
import bleak
from bleak import BleakClient

print(bleak.__file__)

async def test():
    _client = BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=("0000ffe5-0000-1000-8000-00805f9b34fb",), timeout=10.0, pair=False,)
    await _client.connect()
    char_val = await _client.read_gatt_char("2A24")
    print(f"Value: {char_val.decode()}")

asyncio.run(test())

console log:

C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py
attempt to call RequestPreferredConnectionParameters method
sleep in
sleep out
Traceback (most recent call last):
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\test.py", line 13, in <module>
    asyncio.run(test())
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 691, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\test.py", line 10, in test
    char_val = await _client.read_gatt_char("2A24")
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py", line 760, in read_gatt_char
    characteristic = _resolve_characteristic(char_specifier, self.services)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py", line 432, in _resolve_characteristic
    raise BleakCharacteristicNotFoundError(char_specifier)
bleak.exc.BleakCharacteristicNotFoundError: Characteristic 2A24 was not found!

Packets captured during this test are attached in archive

win11_no_error_with_sleep.zip

[dlech]

Does it work if you replace all of that with just an await asyncio.sleep(1)?

[DaLLuZZ]

I guess 1 second is too short interval

--- a/bleak/backends/winrt/client.py
+++ b/bleak/backends/winrt/client.py
@@ -366,6 +366,9 @@ class BleakClientWinRT(BaseBleakClient):
                 # Instead it has the concept of a GATT session that is owned
                 # by the calling program.
                 self._session.maintain_connection = True
+
+                await asyncio.sleep(10)
+
                 # This keeps the device connected until we set maintain_connection = False.

                 cache_mode = None

tried:
await asyncio.sleep(1) - [WinError -2147024874]
await asyncio.sleep(10) - bleak.exc.BleakCharacteristicNotFoundError: Characteristic 2A24 was not found!

code for testing remained the same

upd: actually, the device has characteristic with uuid 0x2A24 and it can be read by android nRF Connect

[dlech]

Oh, so it just breaks in a different way rather than actually fixing it.

I will look at the packet capture later.

[DaLLuZZ]

No, the insertion of delay actually fixed the issue. I just forgot to change service uuid in my test python code, so it caused bleak.exc.BleakCharacteristicNotFoundError: Characteristic 2A24 was not found! error

Finally I successfully read this characteristic value on Windows 11 as central device with the same peripheral device

[dlech]

Very strange.

I would accept a patch that adds a delay_before_get_services parameter to WinRTClientArgs to let you work around this without having to hack Bleak.

[DaLLuZZ]

One more strange thing, now if I remove delay completely (in fact use original bleak v3.0.1), I can still connect and read characteristic value. Probably because services are cached by windows, so windows does not actually getting them again

import asyncio
import bleak
from bleak import BleakClient

vendor_char = "0000ffe5-0000-1000-8000-00805f9b34fb"
device_information = "0000180A-0000-1000-8000-00805f9b34fb"
generic_access = "00001800-0000-1000-8000-00805f9b34fb"

async def test():
    _client = BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=(generic_access,), timeout=10.0, pair=False,)
    await _client.connect()
    char_val = await _client.read_gatt_char("2A00")
    print(f"Value: {char_val.decode()}")

asyncio.run(test())

console log:

C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d>python test.py
C:\Users\khrusas\DEPREPOS\bleak-3.0.1-d\bleak\__init__.py
Value: ITE Peripheral

I will check how to flush the cached services and continue testing

win11_no_error_without_delay.zip

[DaLLuZZ]

I found that Windows 11 WinRT throws the error PermissionError: [WinError -2147024874] The device does not recognize the command quite randomly. But there is at least one reliable way to increase the probability of reproducing the issue on Windows 11 with my peripheral device: the only service provided in tuple for instantiation of BleakClient class object should be "0000ffe5-0000-1000-8000-00805f9b34fb", which is vendor-specific service of the peripheral device:

In this case the probability of fail becomes very close to 100%, so the following testing code will fail with error coming from WinRT of Windows 11 if delay is not inserted in bleak:

import asyncio
import bleak
from bleak import BleakClient

print(bleak.__file__)

vendor_service = "0000ffe5-0000-1000-8000-00805f9b34fb"
device_information = "0000180A-0000-1000-8000-00805f9b34fb"
generic_access = "00001800-0000-1000-8000-00805f9b34fb"

async def test():
    _client = BleakClient(address_or_ble_device="5C:53:10:5A:DF:CD", services=(vendor_service,), timeout=10.0, pair=False,)
    await _client.connect()
    char_val = await _client.read_gatt_char("2A24")
    print(f"Value: {char_val.decode()}")

asyncio.run(test())

Two ways that actually allow me to solve the issue:

1. if I add all available services to tuple, I will most likely connect to Peripheral device without error from WinRT and even without hacked delay before get services in winrt/client.py, using just clear bleak v3.0.1. The probability of getting error decreases as I increase the number of elements in tuple services (provide more services to get)
2. if I add a delay of 1 second to bleak and keep vendor_service the only service in tuple, I will probably connect successfully, but sometimes I will get the same error from WinRT. The probability of getting error decreases significantly as I increase delay value