Universal Application + Bluetooth + SPP

Question

I am currently trying to build a library for using the Serial Port Profile (SPP) on an Universal App.

As far as I have discovered, SPP runs on top of RFCOMM. The basics for RFCOMM are outlined in the MSDN which is fine. I was also able to "find" my device and "connect" to it. I was also able to create a StreamReader and StreamWriter for the RFCOMM.

Now the troubles arise. I understand that RFCOMM provides some kind of channels for various features/tasks, one of them being probably SPP (I know the device features SPP and it even works when done via a "normal" serial connection).

I would like to know if there was an example which bytes I have to send through that channel to get a single byte output on the other side. Is there some kind of connection setup required (bi-directional exchange)? Are there examples for these data packets, what are their names and is there a specific specification for it. I think I would be happy even with some of the correct terms to search for.

Answer 1

Alright, what I assumed was basically wrong. Here is the minimalistic code for a very simple (no error handling, no tasks, ...) communication.

This goes into the Package.appxmanifest:

<Capabilities>
  <m2:DeviceCapability Name="bluetooth.rfcomm">
    <m2:Device Id="any">
      <m2:Function Type="name:serialPort" />
    </m2:Device>
  </m2:DeviceCapability>
</Capabilities>

And this to a method of your choice (make sure your Bluetooth device has been paired, my device has the name "HC-06").

// Find the device
var bluetoothDevicesSpp = await DeviceInformation.FindAllAsync(RfcommDeviceService.GetDeviceSelector(RfcommServiceId.SerialPort));
var bluetoothDeviceHc06 = bluetoothDevicesSpp.SingleOrDefault(d => d.Name == "HC-06");
var serviceRfcomm = await RfcommDeviceService.FromIdAsync(bluetoothDeviceHc06.Id);
StreamSocket socket = new StreamSocket();
await socket.ConnectAsync(serviceRfcomm.ConnectionHostName, serviceRfcomm.ConnectionServiceName, SocketProtectionLevel.BluetoothEncryptionAllowNullAuthentication);
DataWriter writer = new DataWriter(socket.OutputStream);
DataReader reader = new DataReader(socket.InputStream);

To read, use this:

await reader.LoadAsync(1);
byte b = reader.ReadByte();
Debug.WriteLine((char)b);

To write, use this:

writer.WriteString("MaM\r\n");
writer.StoreAsync();

The bytes will be transferred as they are, no additional protocol or similar is necessary. Enjoy.