AndroidBlueToothService.cs

private BluetoothSocket BSocketPadrao { get; set; }

public void AbreConexao()
{
    //Identifica a impressora definada como padrão no configurador do aplicativo
    System.String ImpPadrao = Application.Current.Properties["ImpPadrao"].ToString();
    BluetoothAdapter adaptador = BluetoothAdapter.DefaultAdapter;
    BluetoothDevice impressora = (from bd in adaptador?.BondedDevices
                                  where bd.Name.Contains(ImpPadrao)
                                  select bd).FirstOrDefault();
    impressora = adaptador.GetRemoteDevice(impressora.Address);
    BluetoothSocket Socket = null;
    //Todas as impressoras do modelo MPT-II (Leopardo A8 e a que é usada na Positiva são MPT-II)
    //Basicamente são a mesma impressora, porem são distribuidos por empresas diferentes, o nome original
    //delas são MPT-II
    Socket = impressora?.
    CreateRfcommSocketToServiceRecord(
    UUID.FromString("00001101-0000-1000-8000-00805f9b34fb"));
    BSocketPadrao = Socket;
    //Abre a conexão com a impressora
    Socket.Connect();
}
//Imprime o texto passado no parametro
public async Task PrintText(string text)
{
    BluetoothSocket Socket = BSocketPadrao;
    //Transforma o texto da classificão em um Array de bit para que possa ser impresso
    byte[] buffer = Encoding.UTF8.GetBytes(text);
    //Justifica todo o texto impresso na esquerda
    string ajustaEsquerda = ComandosImpressora.ESCQ + "a" + (char)0;
    byte[] ajustEsquerdaBytes = Encoding.UTF8.GetBytes(ajustaEsquerda);
    await Socket.OutputStream.WriteAsync(ajustEsquerdaBytes, 0, ajustEsquerdaBytes.Length);
    byte[] fonte = { ComandosImpressora.B_ESC, 0x21, ComandosImpressora.FONT_32PX };
    await Socket.OutputStream.WriteAsync(fonte, 0, fonte.Length);
    //Envia o texto da classificação em bits para a impressora
    await Socket.OutputStream.WriteAsync(buffer, 0, buffer.Length);
}

//Lista todos os dispositivos bluetooth pareados com o celular
public IList<string> GetDeviceList()
{
    using (BluetoothAdapter bluetoothAdapter = BluetoothAdapter.DefaultAdapter)
    {
        var btdevice = bluetoothAdapter?.BondedDevices.Select(i => i.Name).ToList();
        return btdevice;
    }
}

public class ComandosImpressora
{
  public static byte FONT_24PX = (byte)0x01;  //24
  public static byte FONT_32PX = (byte)0x00;
  public static byte FONT_24PX_UNDERLINE = (byte)0x81;
  public static byte FONT_32PX_UNDERLINE = (byte)0x80;
  public static byte FONT_48PX_HEIGHT = (byte)0x12;
  public static byte FONT_48PX_HEIGHT_UNDERLINE = (byte)0x92;
  public static byte FONT_48PX_WIDTH = (byte)0x21;
  public static byte FONT_48PX_WIDTH_UNDERLINE = (byte)0xA1;
  public static byte FONT_64PX_HEIGHT = (byte)0x10;
  public static byte FONT_64PX_HEIGHT_UNDERLINE = (byte)0x90;
  public static byte FONT_64PX_WIDTH = (byte)0x20;
  public static byte FONT_64PX_WIDTH_UNDERLINE = (byte)0xA0;
  public static byte FONT_64PX = (byte)0x30;
  public static byte FONT_64PX_UNDERLINE = (byte)0xB0;
  public static byte FONT_48PX = (byte)0x31;
  public static byte FONT_48PX_UNDERLINE = (byte)0xB1;


  public static byte Align_LEFT = (byte)0x30;
  public static byte Align_CENTER = (byte)0x31;
  public static byte Align_RIGHT = (byte)0x32;

  public static int Leopard_Alinha_Esquerda = 0x00;
  public static int Leopard_Alinha_Centro = 0x01;
  public static int Leopard_Alinha_Right = 0x02;

  public static byte LANGUAGE_ENGLISH = 0;
  public static byte LANGUAGE_FRANCE = 1;
  public static byte LANGUAGE_GERMANY = 2;
  public static byte LANGUAGE_UK = 3;
  public static byte LANGUAGE_DENMARK1 = 4;
  public static byte LANGUAGE_SWEDEN = 5;
  public static byte LANGUAGE_ITALY = 6;
  public static byte LANGUAGE_SPAIN1 = 7;
  public static byte LANGUAGE_NORWAY = 8;
  public static byte LANGUAGE_DENMARK2 = 9;
  public static byte LANGUAGE_SPAIN2 = 10;
  public static byte LANGUAGE_PORTUGUESE = 11;
  public static byte LANGUAGE_CHINESE = 48;


  public static int TYPE_IMAGE = 2;
  public static int TYPE_IDLE_TIME = 3;
  public static int TYPE_POWEROFF_TIME = 4;
  public static int TYPE_ALIGN_LEFT = 5;
  public static int TYPE_ALIGN_CENTER = 6;
  public static int TYPE_ALIGN_RIGHT = 7;
  public static int TYPE_ALIGN_FONTMULTIPLE = 8;

  // add decode and encode
  public static byte B_SOF = (byte)0xc0;
  public static byte B_EOF = (byte)0xc1;
  public static byte B_TRANSFER = (byte)0x7D;
  public static byte B_XOR = (byte)0x20;
  public static byte B_ESC = (byte)0x1B;

  //Comandos da Leopardo A8
  public static byte HT = 0x9;
  public static byte LF = 0x0A;
  public static byte CR = 0x0D;
  public static byte ESC = 0x1B;
  public static byte DLE = 0x10;
  public static byte GS = 0x1D;
  public static byte FS = 0x1C;
  public static byte STX = 0x02;
  public static byte US = 0x1F;
  public static byte CAN = 0x18;
  public static byte CLR = 0x0C;
  public static byte EOT = 0x04;

  public static byte ESC_CHAR = 0x1B;
  public static byte[] LINE_FEED = new byte[] { 0x0A };
  public static byte[] CUT_PAPER = new byte[] { GS, 0x56, 0x00 };
  public static byte[] INIT_PRINTER = new byte[] { ESC_CHAR, 0x40 };
  public static byte[] SET_LINE_SPACE_24 = new byte[] { ESC_CHAR, 0x33, 24 };
  public static byte[] SET_LINE_SPACE_30 = new byte[] { ESC_CHAR, 0x33, 30 };

  public static byte[] INIT = { 27, 64 };

  public static byte[] FEED_LINE = { 10 };

  public static byte[] SELECT_FONT_A = { 27, 33, 0 };

  public static byte[] HEADER_FONT = { 27, 33, 32 };

  public static int ALIGN_LEFT = 0;
  public static int ALIGN_CENTER = 1;
  public static int ALIGN_RIGHT = 2;
  public static int BARCODE_UPCA = 65;
  public static int BARCODE_UPCE = 66;
  public static int BARCODE_EAN13 = 67;
  public static int BARCODE_EAN8 = 68;
  public static int BARCODE_CODE39 = 69;
  public static int BARCODE_ITF = 70;
  public static int BARCODE_CODABAR = 71;
  public static int BARCODE_CODE93 = 72;
  public static int BARCODE_CODE128 = 73;
  public static int BARCODE_PDF417 = 74;
  public static int BARCODE_CODE128AUTO = 75;
  public static int BARCODE_EAN128 = 76;
  public static int HRI_NONE = 0;
  public static int HRI_ABOVE = 1;
  public static int HRI_BELOW = 2;
  public static int HRI_BOTH = 3;
  public static int PAGE_LEFT = 0;
  public static int PAGE_BOTTOM = 1;
  public static int PAGE_RIGHT = 2;
  public static int PAGE_TOP = 3;
  public static int FILL_WHITE = 0;
  public static int FILL_BLACK = 1;
  public static int FILL_INVERTED = 2;
  public static int SETTINGS_BLUETOOTH = 5;



  //Convert ASCII/Decimal
  public static string ESCQ = Convert.ToString((char)27);
  public static string GSQ = Convert.ToString((char)29);
  public static string center = ESCQ + "a" + (char)1; //align center
  public static string left = ESCQ + "a" + (char)0; //align left
  public static string bold_on = ESCQ + "E" + (char)1; //turn on bold mode
  public static string bold_off = ESCQ + "E" + (char)0; //turn off bold mode
  public static string cut = ESCQ + "d" + (char)1 + GS + "V" + (char)66; //add 1 extra line before partial cut
  public static string initp = ESCQ + (char)64; //initialize printer
}