GattCharacteristic.WriteValueAsync Method is directly throwing the exception when called after the BLE device is disconnected.

Question

GattCharacteristic.WriteValueAsync Method is directly throwing the exception when called after the BLE device is disconnected.

Punith P 0

I am trying to build the console application to interact with BLE device and I am referring to windows BLE sample UWP program.

GattCharacteristic.WriteValueAsync Method works perfectly fine when BLE device is connected. But directly goes to "hresult_error" when called after device is disconnected. This is observed in the console application that I am building. Where as in the sample program it works fine by returning the failed status.

I have attached the code and call stack image.

BLE_Write_Error

Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-09-25T02:56:17.3033333+00:00

Have you tried to catch exception when use GattCharacteristic.WriteValueAsync? Could you please tell us what is the error code returned?

Punith P 0

I am not getting the error message. It is directly triggering the throw even after using the try-catch in the function. I have attached the call stack image in the previous post.

One small correction I am using GattCharacteristic.WriteValueWithResultAsync.

Not sure why the code is not visible in previous post but I have attached it below:

IAsyncOperation<bool> Write_Data(GattCharacteristic *gatt_charst, char *data, uint16_t size)
{
	hstring tx_data = to_hstring(data);
	//hstring tx_data = L"12345";
	if (!tx_data.empty())
	{
		IBuffer writeBuffer = CryptographicBuffer::ConvertStringToBinary(tx_data, BinaryStringEncoding::Utf8);
		try
		{
			// BT_Code: Writes the value from the buffer to the characteristic.
			GattWriteResult result = co_await gatt_charst->WriteValueWithResultAsync(writeBuffer);

			if (result.Status() == GattCommunicationStatus::Success)
			{
				co_return true;
			}
			else
			{
				cout << "Write failed: Status: " << (int32_t)result.Status() << endl;
				co_return false;
			}
		}
		catch (hresult_error& ex)
		{
			if (ex.code() == E_BLUETOOTH_ATT_INVALID_PDU)
			{
				co_return false;
			}
			if (ex.code() == E_BLUETOOTH_ATT_WRITE_NOT_PERMITTED || ex.code() == E_ACCESSDENIED)
			{
				// This usually happens when a device reports that it support writing, but it actually doesn't.
				co_return false;
			}
			throw;
		}
}

Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-09-25T08:18:50.4766667+00:00

I am not getting the error message. It is directly triggering the throw even after using the try-catch in the function.

I suggest you could try to use debug mode. Refer to the thread: https://github.com/MicrosoftDocs/winrt-api/issues/2241
Punith P 0 Reputation points

2023-09-25T11:56:13.6733333+00:00

It worked Thank you.