Delphi Bluetooth android

Bonjour, j'ai différentes fonctions SendData et ReceiveData et j'aimerai faire en sorte que la fonction ReceiveData me retourne la valeur String seulement quand on lui envoie un truc. Un peu comme le while(Serial3.available()) de l'arduino.
Code:
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function TBTMethod.SendData( nPair:integer; sData:string ) : Boolean;
var
  ToSend: TBytes;
  LDevice: TBluetoothDevice;
begin
  result := FALSE;
  if ManagerConnected then
  try
    if (FSocket = nil) or ( ItemIndex <> nPair ) then
    begin
      if nPair > -1 then
      begin
        //-----------Pour la connexion
        LDevice := FPairedDevices[ nPair ] as TBluetoothDevice;
        FSocket := LDevice.CreateClientSocket( StringToGUID( FServiceGUID ), False);
        //-----------Pour la connexion
        if FSocket <> nil then
        begin
          ItemIndex := nPair;
          FSocket.Connect;
          ToSend := TEncoding.UTF8.GetBytes( sData );
          FSocket.SendData(ToSend);  // FSocket.ReceiveData
          result := TRUE;
        end
        else
          ShowMessage('Out of time -15s-');
      end
      else
        ShowMessage('No paired device selected');
    end
 
    else
    begin
      ToSend := TEncoding.UTF8.GetBytes( sData );
      FSocket.SendData(ToSend);
      result := TRUE;
    end;
 
  except
      on E : Exception do
      begin
        ShowMessage(E.Message);
        FreeAndNil(FSocket);
      end;
    end;
end;
 
//---------------------------------------------------------------------------------------
// nPair : Paired Device List No
function TBTMethod.Receivedata( nPair:integer) : String ;
var
  ToReceive: TBytes;
  StrReceive : String;
  LDevice: TBluetoothDevice;
begin
  result := '';
  if ManagerConnected then
  try
    if (FSocket = nil) or ( ItemIndex <> nPair ) then
    begin
      if nPair > -1 then
      begin
        //-----------Pour la connexion
        LDevice := FPairedDevices[ nPair ] as TBluetoothDevice;
        FSocket := LDevice.CreateClientSocket( StringToGUID( FServiceGUID ), False);
        //-----------Pour la connexion
        if FSocket <> nil then
        begin
          ItemIndex := nPair;
          FSocket.Connect;
//          ToReceive := TEncoding.UTF8.GetBytes( sData );
          ToReceive := FSocket.ReceiveData;;  //TBytes
          //StrReceive := ByteToStr(ToReceive);
          StrReceive := TEncoding.UTF8.GetString(ToReceive);
          result := StrReceive;                                    //Probleme renvoie un 3??????? en plus
        end
        else
          ShowMessage('Out of time -15s-Sorry-');
      end
      else
        ShowMessage('No paired device selected');
    end
 
    else
    begin
      ToReceive := FSocket.ReceiveData;;  // FSocket.ReceiveData
      StrReceive := ByteToStr(ToReceive);
      result := StrReceive;
    end;
 
  except
      on E : Exception do
      begin
        ShowMessage(E.Message);
        FreeAndNil(FSocket);
      end;
    end;
end;