C++/WinRT GetGattServicesAsync() 在 MFC 应用程序中没有响应

Question

C++, WinRT, VS2017 MFC, Win10

I have a C++/WinRT VS2017 console app as a test platform to find my Bluetooth LE device, enumerate the services and characteristics, and then write a value to the Tx characteristic, etc. I have all of that working and now I am trying to move that code to an existing VS2017 MFC app.

In the console app the BluetoothLEAdvertisementWatcher and callback to the watcher.Received() were done in the main.cpp. Once my BLE device was found, a separate function was called to create the device object from the deviceAddress and then enumerate the services and characteristics.

In the MFC app I created a separate function run in a separate thread to establish the watcher and attach the callback. That all works fine up to the point that it needs to GetGattServicesAsync(). In the console app the function OpenDevice() used to create the device object and get the services was done with a get() as in:

OpenDevice(deviceAddress).get(); 

The first thing OpenDevice() does is create the device object using

auto device = co_await BluetoothLEDevice::FromBluetoothAddressAsync(deviceAddress);

If the device object is created, then the next thing it did was get the Services with:

auto services = co_await device.GetGattServicesAsync();

Here is where my MFC code fails. In the function thread that creates the watcher and watcher.Received callback my MFC code does the same call to OpenDevice(). In OpenDevice the device object is indeed created but then the call to GetGattServicesAsync() will never finish so matter how long I wait. If I enter the GetGattServicesAsync() in Debug mode, however, then it works fine.

For testing I have also put the OpenDevice() code within the watcher thread but, again, it stalls on GetGattServicesAsync(). In this case, however, I cannot use the co_await but had to use

auto services = device.GetGattServicesAsync().get();

Regardless, the GetGattServicesAsync() never finished.

Any suggestions of what I need to do or what I am doing wrong?

Answer 1

Since running in Debug was working I was trying to solve why this was not working in Release mode. I was relying on my log file entries to track the progress after the fact. For the halibut I put in some Beeps() to let me hear the progress and I was hearing beeps but not seeing log entries after that GetGattServicesAsync(). Apparently what was happening is that, for what ever reason, the GetGattServicesAsync() was NULLing out the handle to my log file so no writes were taking place. I did a check for NULL after the GetGattServicesAsync() and, if it was, re-established the log file. All of a sudden my log file was showing the progress that I thought was not happening. Sometime I think it is just me...:-(