import com.harrysoft.androidbluetoothserial.BluetoothManager;

// Setup our BluetoothManager
BluetoothManager bluetoothManager = BluetoothManager.getInstance();
if (bluetoothManager == null) {
    // Bluetooth unavailable on this device :( tell the user
    Toast.makeText(context, "Bluetooth not available.", Toast.LENGTH_LONG).show(); // Replace context with your context instance.
    finish();
}

Collection<BluetoothDevice> pairedDevices = bluetoothManager.getPairedDevices();
for (BluetoothDevice device : pairedDevices) {
    Log.d("My Bluetooth App", "Device name: " + device.getName());
    Log.d("My Bluetooth App", "Device MAC Address: " + device.getAddress());
}

import com.harrysoft.androidbluetoothserial.BluetoothSerialDevice;

private SimpleBluetoothDeviceInterface deviceInterface;

private void connectDevice(String mac) {
    bluetoothManager.openSerialDevice(mac)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(this::onConnected, this::onError);
}

private void onConnected(BluetoothSerialDevice connectedDevice) {
    // You are now connected to this device!
    // Here you may want to retain an instance to your device:
    deviceInterface = connectedDevice.toSimpleDeviceInterface();
    
    // Listen to bluetooth events
    deviceInterface.setListeners(this::onMessageReceived, this::onMessageSent, this::onError);
    
    // Let's send a message:
    deviceInterface.sendMessage("Hello world!");
}

private void onMessageSent(String message) {
    // We sent a message! Handle it here.
    Toast.makeText(context, "Sent a message! Message was: " + message, Toast.LENGTH_LONG).show(); // Replace context with your context instance.
}

private void onMessageReceived(String message) {
    // We received a message! Handle it here.
    Toast.makeText(context, "Received a message! Message was: " + message, Toast.LENGTH_LONG).show(); // Replace context with your context instance.
}

private void onError(Throwable error) {
    // Handle the error
}

// Please remember to destroy your instance after closing as it will no longer function!

// Disconnect one device
bluetoothManager.closeDevice(macAddress); // Close by mac
// OR
bluetoothManager.closeDevice(connectedDevice); // Close by device instance
// OR
bluetoothManager.closeDevice(deviceInterface); // Close by interface instance

// Disconnect all devices
bluetoothManager.close();