c＃蓝牙LE-写入配置错误-从未调用过ValueChanged

Question

So I try to connect my c# WPF program to a BLE device and this is the code to connect to the device:

private async Task ConnectToWatcher(DeviceInformation deviceInfo) {
        try {
            // get the device
            BluetoothLEDevice device = await BluetoothLEDevice.FromIdAsync(deviceInfo.Id);

            // get the GATT service
            Thread.Sleep(150);
            var gattServicesResult = await device.GetGattServicesForUuidAsync(new Guid(RX_SERVICE_UUID));
            service = gattServicesResult.Services[0];

            // get the GATT characteristic
            Thread.Sleep(150);
            var gattCharacteristicsResult = await service.GetCharacteristicsForUuidAsync(new Guid(RX_CHAR_UUID));
            characteristic = gattCharacteristicsResult.Characteristics[0];

            // register for notifications
            Thread.Sleep(150);

            characteristic.ValueChanged += (sender, args) => {
                Debug.WriteLine($"[{device.Name}] Received notification containing {args.CharacteristicValue.Length} bytes");
            };

            GattWriteResult result =
            await characteristic.WriteClientCharacteristicConfigurationDescriptorWithResultAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
            Debug.WriteLine($"Characteristics write result: status={result.Status}, protocolError={result.ProtocolError}");

        } catch (Exception ex) when ((uint)ex.HResult == 0x800710df) {
            Debug.WriteLine("bluetooth error 1");
            // ERROR_DEVICE_NOT_AVAILABLE because the Bluetooth radio is not on.
        }
    }

The line

 Debug.WriteLine($"Characteristics write result: status={result.Status}, protocolError={result.ProtocolError}"

creates the output Characteristics write result: status=protocolError, protocolError=3 I couldn't find anywhere whats that supposed to mean. The effect is the Method characteristic.ValueChanged never gets called.

Do I have to do more to have the characteristic configurated? And has anybody any idea why the method isn't called or what that error message means?

Thanks a bunch.

Answer 1

Apparently, some Windows 10 builds have a COM security bug. Solution was to register for Windows-Insider-Program and update Windows.

Update: There are two more solutions to this: 1) Calling CoInitializeSecurity from outside your c#-code (didn't bring it to work) - or- 2) Writing two new keys into the windows registry. You cann create a file "Bluetooth.reg", which will add those two keys on a doubleklick. This answer from https://social.msdn.microsoft.com/Forums/en-US/58da3fdb-a0e1-4161-8af3-778b6839f4e1/bluetooth-bluetoothledevicefromidasync-does-not-complete-on-10015063?forum=wdk was my solution:

Hi Kamen, I have experienced exactly same issue. You can give a quick try of the following:

---

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\\SOFTWARE\\Classes\\AppID{C6BFD646-3DF0-4DE5-B7AF-5FFFACB844A5}] "AccessPermission"=hex:01,00,04,80,9c,00,00,00,ac,00,00,00,00,00,00,00,14,00,\\ 00,00,02,00,88,00,06,00,00,00,00,00,14,00,07,00,00,00,01,01,00,00,00,00,00,\\ 05,0a,00,00,00,00,00,14,00,03,00,00,00,01,01,00,00,00,00,00,05,12,00,00,00,\\ 00,00,18,00,07,00,00,00,01,02,00,00,00,00,00,05,20,00,00,00,20,02,00,00,00,\\ 00,18,00,03,00,00,00,01,02,00,00,00,00,00,0f,02,00,00,00,01,00,00,00,00,00,\\ 14,00,03,00,00,00,01,01,00,00,00,00,00,05,13,00,00,00,00,00,14,00,03,00,00,\\ 00,01,01,00,00,00,00,00,05,14,00,00,00,01,02,00,00,00,00,00,05,20,00,00,00,\\ 20,02,00,00,01,02,00,00,00,00,00,05,20,00,00,00,20,02,00,00

[HKEY_LOCAL_MACHINE\\SOFTWARE\\Classes\\AppID\\YOURAPP.exe] "AppID"="{C6BFD646-3DF0-4DE5-B7AF-5FFFACB844A5}"

---

1. Copy above content to a text file.

2. Replace 'YOURAPP.EXE' with your executable name

3. Optionally replace GUIDs (I have created a new one for you)

4. Save text file with an extension as .reg

5. Double click on the file.

6. You would see a message 'The Keys and values contained in ..... .reg have been successfully added to the registry.'

With this, I don't need to call CoInitializeSecurity from my app.

Answer 2

you need to call CoInitializeSecurity before

more info here. couple of weeks I spent looking for solution :)

https://social.msdn.microsoft.com/Forums/en-US/58da3fdb-a0e1-4161-8af3-778b6839f4e1/