Can't advertise on bluetooth - xamarin

Question

I want to create a Gatt Server in my Xamarin.Forms app so that other devices can scan for it via bluetooth. I am using this plugin:
https://github.com/aritchie/bluetoothle
This is my code to create a Gatt Server and advertise data:
server = CrossBleAdapter.Current.CreateGattServer();
var service = server.AddService(serviceGuid, true);
var characteristic = service.AddCharacteristic(
characteristicGuid,
CharacteristicProperties.Read |
CharacteristicProperties.Write | CharacteristicProperties.WriteNoResponse,
GattPermissions.Read | GattPermissions.Write
);
var notifyCharacteristic = service.AddCharacteristic
(
notifyCharacteristicGuid,
CharacteristicProperties.Indicate | CharacteristicProperties.Notify,
GattPermissions.Read | GattPermissions.Write
);
IDisposable notifyBroadcast = null;
notifyCharacteristic.WhenDeviceSubscriptionChanged().Subscribe(e =>
{
var #event = e.IsSubscribed ? "Subscribed" : "Unsubcribed";
if (notifyBroadcast == null)
{
notifyBroadcast = Observable
.Interval(TimeSpan.FromSeconds(1))
.Where(x => notifyCharacteristic.SubscribedDevices.Count > 0)
.Subscribe(_ =>
{
Debug.WriteLine("Sending Broadcast");
var dt = DateTime.Now.ToString("g");
var bytes = Encoding.UTF8.GetBytes("SendingBroadcast");
notifyCharacteristic.Broadcast(bytes);
});
}
});
characteristic.WhenReadReceived().Subscribe(x =>
{
var write = "HELLO";
// you must set a reply value
x.Value = Encoding.UTF8.GetBytes(write);
x.Status = GattStatus.Success; // you can optionally set a status, but it defaults to Success
});
characteristic.WhenWriteReceived().Subscribe(x =>
{
var write = Encoding.UTF8.GetString(x.Value, 0, x.Value.Length);
Debug.WriteLine("in WhenWriteReceived() value: " + write);
// do something value
});
await server.Start(new AdvertisementData
{
LocalName = "DariusServer",
ServiceUuids = new List<Guid>() { serverServiceGuid }
});
I am using this app to scan for my advertisement data:
https://play.google.com/store/apps/details?id=no.nordicsemi.android.mcp
I can't discover my app with it. I don't know what I'm doing wrong? I am testing with a real device, SM-T350 tablet

Answer 1

I spent countless hours to get this plugin to work with no luck. But this native code works for anyone else who has the same problem:
private async Task AndroidBluetooth()
{
try
{
await Task.Delay(5000); // just to make sure bluetooth is ready to go, this probably isn't needed, but good for peace of mind during testing
BluetoothLeAdvertiser advertiser = BluetoothAdapter.DefaultAdapter.BluetoothLeAdvertiser;
var advertiseBuilder = new AdvertiseSettings.Builder();
var parameters = advertiseBuilder.SetConnectable(true)
.SetAdvertiseMode(AdvertiseMode.Balanced)
//.SetTimeout(10000)
.SetTxPowerLevel(AdvertiseTx.PowerHigh)
.Build();
AdvertiseData data = (new AdvertiseData.Builder()).AddServiceUuid(new ParcelUuid(Java.Util.UUID.FromString("your UUID here"))).Build();
MyAdvertiseCallback callback = new MyAdvertiseCallback();
advertiser.StartAdvertising(parameters, data, callback);
}
catch(Exception e)
{
}
}
public class MyAdvertiseCallback : AdvertiseCallback
{
public override void OnStartFailure([GeneratedEnum] AdvertiseFailure errorCode)
{
// put a break point here, in case something goes wrong, you can see why
base.OnStartFailure(errorCode);
}
public override void OnStartSuccess(AdvertiseSettings settingsInEffect)
{
base.OnStartSuccess(settingsInEffect);
}
}
}
Just to note, it wouldn't work if if I included the device name, because the bluetooth transmission would be too large in that case with a service UUID (max 31 bytes I believe).