How to disconnect a BLE device after successful connection

Prajnith Kumar 0

I have successfully connected to BLE device by using BluetoothLEDevice.FromIdAsync(deviceInfo.Id) and bluetoothLeDevice.GetGattServicesAsync(BluetoothCacheMode.Cached) API's in unpaired mode over Windows 10 with .NET Framework 4.7.2 but I was unsuccessful in disconnecting from the BLE device even with the dispose code listed below and also clearing the characteristics. How do I correctly close the BLE connection?

            try

            {

                var services = Task.Run(async () => await bluetoothLeDevice.GetGattServicesAsync()).Result;

                foreach (var service in services.Services)

                {

                    service?.Session?.Dispose();

                    service?.Dispose();

                }

            }

            catch (Exception ex)

            {

                Debug.WriteLine(ex.Message);

            }

            bluetoothLeDevice?.Dispose();

            int n = 0;

            while (bluetoothLeDevice.ConnectionStatus != BluetoothConnectionStatus.Disconnected)

            {

                Task.Run(async () => Thread.Sleep(1000)); // Wait for the device to disconnect

                Debug.WriteLine($"Checking Disconnection Status!, Delay Seconds: {n}");

                n++;

            }

            bluetoothLeDevice = null;
```Thanks in Advance!

Prajnith

Junjie Zhu - MSFT 16,151 Reputation points Microsoft Vendor

2024-06-14T02:28:04.66+00:00

Hi @Prajnith Kumar ，

Welcome to Microsoft Q&A!

You are using Windows 10 with .NET Framework 4.7.2, Because different types of projects have different solutions, so what is your project, UWP or WPF?

Thank you.

Prajnith Kumar 0

Hi @Junjie Zhu - MSFT
I use WPF.
I forgot to mention previously that also I tried to turn off Bluetooth using below code but I got "DeniedByUser" result.

        var radioReq = Task.Run(async () => await Radio.RequestAccessAsync()).Result;

        var radios = Task.Run(async () => await Radio.GetRadiosAsync()).Result;

        var radSetState = Task.Run(async () => await radios[0].SetStateAsync(RadioState.Off)).Result;

Junjie Zhu - MSFT 16,151 Reputation points Microsoft Vendor

2024-06-17T06:43:21.58+00:00

Hi @Prajnith Kumar ，

Welcome to Microsoft Q&A!

For desktop APP, it can use the win32 API IOCTL_BTH_DISCONNECT_DEVICE IOCTL in DeviceIoControl to disconnect a BLE device.

Thank you.

Prajnith Kumar 0

Hi @Junjie Zhu - MSFT **
Below is the code I tried to disconnect the BLE device, and I got the error code 0x0000048f, I'm running the project in elevated user permission.

    const int IOCTL_BTH_DISCONNECT_DEVICE = 0x41000c;

    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]

    internal static extern bool DeviceIoControl(
    IntPtr hDevice,
    uint dwIoControlCode,
    ref long InBuffer,
    int nInBufferSize,
    IntPtr OutBuffer,
    int nOutBufferSize,
    out int pBytesReturned,
    IntPtr lpOverlapped);


                    var r = BluetoothRadio.PrimaryRadio;
                    var h = r.Handle;
                    long btAddr = BluetoothAddress.Parse("48:02:af:16:72:82").ToInt64();
                    int bytesReturned = 0;
                    var success = DeviceIoControl(h,
                    IOCTL_BTH_DISCONNECT_DEVICE,
                    ref btAddr, 8,
                    IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);
                    if (!success)
                    {
                        int gle = Marshal.GetLastWin32Error();
                        Debug.WriteLine(string.Format(CultureInfo.InvariantCulture, "failure: {0} = 0x{0:X}.", gle));
                    }
                    else
                    {
                        Debug.WriteLine("Success !");
                    }

Thank you

Junjie Zhu - MSFT 16,151 Reputation points Microsoft Vendor

2024-06-18T01:51:05.74+00:00

Hi @Prajnith Kumar ，

The current question relates to the use of WPF and the win32 API, I've changed the tag for the question, and there will be WPF engineers to help you later.
Hui Liu-MSFT 46,961 Reputation points Microsoft Vendor

2024-06-18T10:21:55.9533333+00:00

Hello, @Prajnith Kumar.

For the original question, there may be some factors affecting.

When you connected a BLE device and access its services and characteristics, there is an active session for your operations. You dispose of the device but the session is still open.

To solve this problem you need do a little more work when disconnecting the device like this:

If you opened a service(GattDeviceService) you need call service?.Dispose(). If you opened a characteristic(GattCharacteristic) you need to call characteristic?.Service?.Dispose(). For checking the session status you can call service?.Session.SessionStatus or characteristic?.Service?.Session.SessionStatus。

I'm still investigating the IOCTL_BTH_DISCONNECT_DEVICE error you're encountering. It will take some time.

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How to disconnect a BLE device after successful connection

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