Windows: `BleakClientWinRT` `_get_services` frequently times out

[gudnimg]

I've tried also tried extending the timeout to 30 seconds. No luck. I'm unsure how to debug this further. When I use nRF Connect for Desktop or the nRF Connect app, discovering services is pretty quick. My peripheral is using Zephyr / NCS 3.1.0 firmware, not sure if that can affect things.

2025-09-19 12:12:40,060 bleak.backends.winrt.scanner DEBUG: 46 devices found. Watcher status: <BluetoothLEAdvertisementWatcherStatus.STOPPED: 3>.
2025-09-19 12:12:40,174 bleak.backends.winrt.client DEBUG: Connecting to BLE device @ [MY BDA]
2025-09-19 12:12:40,237 bleak.backends.winrt.client DEBUG: getting services (service_cache_mode=None, cache_mode=None)...
2025-09-19 12:13:10,253 bleak.backends.winrt.client DEBUG: closing requester
2025-09-19 12:13:10,256 bleak.backends.winrt.client DEBUG: closing session

Some info about my setup:

• Windows 11 24H2 (26100.6584)
• BLE dongle: https://www.tp-link.com/nordic/home-networking/adapter/ub500/
• Python 3.13.7
• Bleak 1.1.1
• winrt: 3.2.1
• pywin32: 311
• (More pip packages relevant?)

Code:

# start the connection, here it hangs on discovering services
async with BleakClient( device, disconnected_handler ) as client:
    # Just some code not relevant to issue

I find the device using await BleakScanner.find_device_by_name and also sometimes await BleakScanner.find_device_by_address. I don't see a difference in behavior when it comes to discovering services.

---

I can debug further and share logs if possible. Any advice how to debug the issue further would be very appreciated! :)

[gudnimg]

I've tracked the issue down to this wait in BleakClientWinRT. Services are actually discovered almost immediately.

# a connection may not be made until we request info from the
# device, so we have to get services before the GATT session
# is set to active
await event.wait()

[dlech]

I saw that there is a potential for a race condition that could cause this. Can you please test #1830 to see if it fixed the problem for you?

[gudnimg]

@dlech It looks like the issue is still present on my end.

[dlech]

The next step would be to capture debug logs and Bluetooth packets as described in the troubleshooting page of the docs.

[gudnimg]

I am having troubling installing the BTP tool. But using Wireshark I get this from the controller:

After 24 seconds the connection is created. Otherwise it was hanging after the LE Set Scan Enable.

I haven't used this tool before, I'll see if I can create a better log for you :)

When the issue happens, on the peripheral side all I can see is there is never a connection established during those "24 seconds". So it looks like Bleak/Windows is doing the waiting, not the peripheral.

[gudnimg]

Similar log except now it also includes the commands HCI_CMD. In this case it hangs for 12 seconds.

[gudnimg]

I wonder if this USB event is related to the issue URB_FUNCTION_SYNC_RESET_PIPE_AND_CLEAR_STALL. I'll try and find time to test this on another computer over the weekend.

[gudnimg]

URB_FUNCTION_SYNC_RESET_PIPE_AND_CLEAR_STALL went away went I disabled the option to allow Windows to power down the Bluetooth dongle. Issue still persists though, the time needed to wait for the connection is quite random. Sometimes 12 seconds, sometimes over 30 seconds.

[dlech]

I haven't used this tool before, I'll see if I can create a better log for you :)

You can do a File > Save in Wireshark and put the file in a .zip and attach it to a comment here on GitHub.

[gudnimg]

I haven't forgotten the issue :). It may take me a few days more.

[gudnimg]

@dlech I managed to install btp (I had to extract the msi installer manually). Running btvs.exe produced the following log in Wireshark:
bleak-wireshark-btp-log.zip

This is not the same computer as before. This computer has an integrated Bluetooth adapter.

The timeout is currently the default (10 seconds).