How to scan Bluetooth Low energy (BLE) devices which are available/present? - windows-10-mobile

Question

I am working on a windows phone app that can scan BLE devices. I have implemented the logic which is showing the desired devices.
But the problem is that if I remove those devices or switch them off, even then my application returns their names in scan result. I think it is returning cached result. How I can make sure it will show only those devices which are available/present.
I have tried using the additional properties i.e. System.Devices.Aep.IsPresent etc in scan but they are coming as null in result no matter ble devices available or not.
Here is code snippet I am using -
string[] requestedProperties = new string[] { "System.Devices.Aep.IsPresent"
, "System.Devices.Present"
, "System.Devices.Connected"
, "System.Devices.Paired"
, "System.Devices.Aep.IsConnected"
, "System.Devices.AepContainer.IsPresent"
};
diCollection = await DeviceInformation.FindAllAsync(GattDeviceService.GetDeviceSelectorFromUuid(serviceUuid)
, requestedProperties
);
foreach (var diItem in diCollection)
{
Debug.WriteLine("Discovered Device name - " + diItem.Name);
Debug.WriteLine("Discovered Device Additional Properties Below");
foreach (var item in diItem.Properties)
{
Debug.WriteLine("Key-{0} Value-{1}", item.Key, item.Value);
}
}
Here is the Package.appxmanifest capabilities used -
<Capabilities>
<Capability Name="internetClientServer" />
<DeviceCapability Name="bluetooth" />
</Capabilities>
Please help me resolve this small issue. Am I missing something trivial here?
Thanks in advance.
-Jitender

Answer 1

I tried every single one of the properties below with 2 PCs, where both were paired to the Handheld and only one was turned on and a Windows Handheld 8.1.
https://learn.microsoft.com/en-us/windows/uwp/devices-sensors/device-information-properties
The ones needed were AssociationEndpoint related properties, none of which are supported in windows phone 8.1 (even the enumeration is not available) - so basically the api does not provide any way for us to be able to query the connections from cache for whether they are presently available or not.
I tested with every combinations and they do not provide sufficient information (the PC that is turned on is indistinguishable from the one that was not).
The only workaround was to connect to every paired computer on the cache and see if each connection was successful to add this to the list displayed if succeeeded. Every failed connection takes ~4-5 seconds. So this can take some significant amount of delay in showing the list if there are multiple paired computers via in the past. Yet I could not find any other feasible way of checking this, at least this resolves the issue.