C＃Windows UWP Gatt服务器：请求对象始终为NULL

Question

我已根据微软文档网站在Windows上实施了GATT服务器：https://docs.microsoft.com/en-us/windows/uwp/devices-sensors/gatt-server

服务器启动，我可以在Android手机上使用不同的蓝牙LE浏览器发现创建的服务和特性。

但是当我在Windows上从客户端向GATT服务器发出读取或写入请求时，我遇到了问题（安装了Creators Update）。

async void ReadCharacteristic_ReadRequested(GattLocalCharacteristic sender, GattReadRequestedEventArgs args) {
  var deferral = args.GetDeferral();

  // Our familiar friend - DataWriter.
  var writer = new DataWriter();
  // populate writer w/ some data. 
  // ... 

  var request = await args.GetRequestAsync();
  request.RespondWithValue(writer.DetachBuffer());

  deferral.Complete();
}

当读取特征值请求进入时，执行上面的代码片段。请求对象始终为NULL。

var request = await args.GetRequestAsync();

有谁知道我做错了什么？为什么请求对象总是为NULL？微软网站上的示例代码是不完整的？ 有人在Windows UWP上有一个GATT服务器的工作示例吗？

提前致谢， 基督教

Answer 1

请参阅官方示例BluetoothLE，服务器代码位于Scenario3_ServerForeground。请参阅其ResultCharacteristic_ReadRequestedAsync方法作为参考。

private async void ResultCharacteristic_ReadRequestedAsync(GattLocalCharacteristic sender, GattReadRequestedEventArgs args)
{
    // BT_Code: Process a read request. 
    using (args.GetDeferral())
    {
        await CoreApplication.MainView.CoreWindow.Dispatcher.RunTaskAsync(async () =>
        {
            // Get the request information.  This requires device access before an app can access the device's request. 
            GattReadRequest request = await args.GetRequestAsync();
            if (request == null)
            {
                // No access allowed to the device.  Application should indicate this to the user.
                rootPage.NotifyUser("Access to device not allowed", NotifyType.ErrorMessage);
                return;
            }

            var writer = new DataWriter();
            writer.ByteOrder = ByteOrder.LittleEndian;
            writer.WriteInt32(resultVal);

            // Can get details about the request such as the size and offset, 
            //as well as monitor the state to see if it has been completed/cancelled externally.
            // request.Offset
            // request.Length
            // request.State
            // request.StateChanged += <Handler>

            // Gatt code to handle the response
            request.RespondWithValue(writer.DetachBuffer());
        });
    }
}

Answer 2

我遇到了同样的问题。事实证明，要发送/接收数据，您需要在Package.appxmanifest文件中的功能下启用蓝牙。

这很明显，但是在我看到的任何教程，CH9视频或文档中都没有指示需要这样做。

希望这可以节省一些时间。