Connect to a Bluetooth Serial Device with Xamarin.Android

I have been exploring the Xamarin tools recently and decided to try my hand at connecting some Bluetooth hardware to Android for a project that will be released soon. I have learned quite a bit about Bluetooth on Android and decided to write up a short description on how to connect to a Bluetooth serial device via RFCOMM/SPP.

First, grab an instance of the default BluetoothAdapter on the Android device and determine if it is enabled:

BluetoothAdapter adapter = BluetoothAdapter.DefaultAdapter;  
if(adapter == null)  
    throw new Exception("No Bluetooth adapter found.");

if(!adapter.IsEnabled)  
    throw new Exception("Bluetooth adapter is not enabled.");

Next, get an instance of the BluetoothDevice representing the physical device you’re connecting to. You can get a list of currently paired devices using the adapter’s BondedDevices collection. I use some simple LINQ to find the device I’m looking for:

BluetoothDevice device = (from bd in adapter.BondedDevices  
                          where bd.Name == "NameOfTheDevice" select bd).FirstOrDefault();

if(device == null)  
    throw new Exception("Named device not found.");</pre>

Finally, use the device’s CreateRfCommSocketToServiceRecord method, which will return a BluetoothSocket that can be used for connection and communication. Note that the UUID specified below is the standard UUID for SPP:

_socket = device.CreateRfcommSocketToServiceRecord(UUID.FromString("00001101-0000-1000-8000-00805f9b34fb"));  
await _socket.ConnectAsync();  

Now that the device is connected, communication occurs via the InputStream and OutputStream properties which live on the BluetoothSocket object These properties are standard .NET Stream objects and can be used exactly as you’d expect:

// Read data from the device
await _socket.InputStream.ReadAsync(buffer, 0, buffer.Length);

// Write data to the device
await _socket.OutputStream.WriteAsync(buffer, 0, buffer.Length);  

That’s it! Now to get things working with iOS…