Windows : Failed to connect to device: Could not get GATT characteristics

[pymenow]

• bleak version: 0.20.2
• Python version: 3.9.13
• Operating System: Windows 11 22621.1635
• BlueZ version (bluetoothctl -v) in case of Linux:

Description

Failed to connect to device: Could not get GATT characteristics for <_bleak_winrt_Windows_Devices_Bluetooth_GenericAttributeProfile.GattDeviceService object at 0x00000206F9189750>: Access Denied

The same code works in Linux but issues seen in windows.

What I Did

Just attempting to connect to the BLE device . Below is the function I am using to connect.

async def omn_connect(address: str, reconnect_delay: int = 5) -> Optional[BleakClient]:
    async def on_disconnect(client, error):
        print(f"Device disconnected, error: {error}")

    try:
        print(f"Attempting to connect to device {address}...")
        client = BleakClient(address, disconnected_callback=lambda _: asyncio.ensure_future(on_disconnect(client, _)))
        await client.connect()
        print("Connected")
        
        return client
    except Exception as e:
        print(f"Failed to connect to device: {e}")
        return None


async def omn_disconnect(client: BleakClient):
    try:
        await client.disconnect()
        print("Disconnected successfully")
    except Exception as e:
        print(f"Disconnection failed: {e}")

Logs

Added logs below .
blelogs.txt

Also added the Wireshark logs :
GATT-Wireshark.zip

[pymenow]

GATT-Wider.zip
Added extended logs for Wireshark where I pair with the device via Windows Bluetooth and then start the bleak script to connect before I run into the same issue.

[dlech]

The program is not complete, so it is impossible to say what could be happening.

Please provide a full minimal reproducible test case.

[pymenow]

Hello here is a fully reproducible test .

import asyncio
from bleak import BleakClient


async def discover_services_and_handles(device_address):
    async with BleakClient(device_address) as client:
        services = await client.get_services()

        for service in services:
            print(f"Service: {service.uuid}")
            for characteristic in service.characteristics:
                print(f"  Characteristic: {characteristic.uuid}, Handle: {characteristic.handle}")

device_address = "XX:XX:XX:XX:XX:XX"  # Replace with your device's address
asyncio.run(discover_services_and_handles(device_address))

[dlech]

Can you please run with the following change so we can see which UUID is causing the problem?

diff --git a/bleak/backends/winrt/client.py b/bleak/backends/winrt/client.py
index 3431d0b..003b3b7 100644
--- a/bleak/backends/winrt/client.py
+++ b/bleak/backends/winrt/client.py
@@ -706,7 +706,7 @@ class BleakClientWinRT(BaseBleakClient):
                 characteristics: Sequence[GattCharacteristic] = _ensure_success(
                     await FutureLike(service.get_characteristics_async(*args)),
                     "characteristics",
-                    f"Could not get GATT characteristics for {service}",
+                    f"Could not get GATT characteristics for {service.uuid} ({service.attribute_handle})",
                 )
 
                 logger.debug("returned from get_characteristics_async")

[pymenow]

Thanks - Here is the output -
bleak.exc.BleakError: Could not get GATT characteristics for 0000181e-0000-1000-8000-00805f9b34fb (68): Access Denied

On linux these are read correctly using the same code.

  - Service: 0000181e-0000-1000-8000-00805f9b34fb
    - Characteristic: 00002aa4-0000-1000-8000-00805f9b34fb
      - Handle: 69
      - Properties: ['read', 'write']
    - Characteristic: 00002aa5-0000-1000-8000-00805f9b34fb
      - Handle: 71
      - Properties: ['read', 'write']

[dlech]

Thanks. Could you please test #1294 to see if it fixed the problem?

[pymenow]

Thanks , was able to connect to the device successfully with this change.
Its likely since 0000181e is a bond management servcie - Windows wants to handle this and hence the restriction ?

[dlech]

Great, thanks for testing! Yes, it seems Windows gives an error for services like this that are "owned" by the OS while other OSes just hide them completely.