BroadcastReceiver for Bluetooth device discovery works on one device but not on another

Code:

I use the following code taken from here with a target API level 23 (and minimum API level 18).

private final BroadcastReceiver mReceiver = new BroadcastReceiver()
{
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();

        if (BluetoothDevice.ACTION_FOUND.equals(action))
        {
            bluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            deviceNameTextView.setText(bluetoothDevice.getName());
        }
    }
};

On a button pressed event I call:

IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter);
mBluetoothAdapter.startDiscovery(); // was initialized successsfully

My AndroidManifest.xml contains:

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

Devices:

1. Samsung Galaxy S III (API level 18)
2. Sony Xperia Z3 (API level 23)

Facts:

• both devices are running the exact same code
• device 1 can discover device 2 (and any other Bluetooth device)
• device 2 cannot discover device 1 (or any other Bluetooth device)
• both devices are discoverable
• tested discoverability with the standard system dialog for pairing for both devices successfully
• both devices were unpaired at all times (I don't want to pair)
• No exceptions are thrown.

What is wrong?

Update 1: Since API level 23 permissions may have to be requested at run time. Yvette pointed me to that, thank you! Unfortunately it didn't solve my problem.

What speaks against her theory is the following:

mBluetoothAdapter.startDiscovery() returns true, which means success (see here).

// Assume thisActivity is the current activity
int permissionCheck = ContextCompat.checkSelfPermission(thisActivity , Manifest.permission.BLUETOOTH_ADMIN);

if(permissionCheck == PackageManager.PERMISSION_GRANTED)
    Log.i("info", "Permission granted!");
else
    Log.i("info", "Permission not granted!");

Running this code with BLUETOOTH_ADMIN and BLUETOOTH returns both times:

Permission granted!

When doing some research, I found the following article from the official documentation regarding changes in Android 6.0 (API level 23).

To access the hardware identifiers of nearby external devices via Bluetooth and Wi-Fi scans, your app must now have the ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION permissions:
- WifiManager.getScanResults()
- BluetoothDevice.ACTION_FOUND
- BluetoothLeScanner.startScan()

So, I was missing the permissions ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION all along. But just adding them in the AndroidManifest.xml file is not enough. You have to request those privileges at run time like Yvette suggested.

You can find here how you can do that or just use this piece of code I wrote to get the permissions needed for Bluetooth discovery.

final int CODE = 5; // app defined constant used for onRequestPermissionsResult

String[] permissionsToRequest =
{
    Manifest.permission.BLUETOOTH_ADMIN,
    Manifest.permission.BLUETOOTH,
    Manifest.permission.ACCESS_FINE_LOCATION,
    Manifest.permission.ACCESS_COARSE_LOCATION
};

boolean allPermissionsGranted = true;

for(String permission : permissionsToRequest)
{
    allPermissionsGranted = allPermissionsGranted && (ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED);
}

if(!allPermissionsGranted)
{
    ActivityCompat.requestPermissions(this, permissionsToRequest, CODE);
}

mBluetoothAdapter.startDiscovery();

This code is assuming that the user grants the permissions (for simplicity). If you want your app to behave differently when the permissions are not granted see "Handle the permissions request response" in this article.