Which SDK to use for Zebra KR203?

I tried to connect to my printer zebra KR203 for Kiosk, I downloaded link-os-sdk.

 

I´m programming with JAVA this is my code, I want to get the printers connected:

 

package logic;

import com.zebra.sdk.comm.ConnectionException;

import com.zebra.sdk.printer.discovery.*;

public class Inicio {

public static void main(String[] args) throws ConnectionException {

        try {

            for (DiscoveredPrinterDriver printer : UsbDiscoverer.getZebraDriverPrinters()) {

                System.out.println(printer);

            }           

            for (DiscoveredUsbPrinter usbPrinter : UsbDiscoverer.getZebraUsbPrinters()) {  // My line 10

                System.out.println(usbPrinter);

            }

        } catch (ConnectionException e) {

            System.out.println("Error discovering local printers: " + e.getMessage());

        }

}

}

 

But when I run my app I get this error:

Exception in thread "main" java.lang.NullPointerException

at com.zebra.sdk.printer.discovery.UsbDiscoverer.getZebraUsbPrinters(Unknown Source)

at logic.Inicio.main(Inicio.java:10).

 

My working directory is "C:\Program Files\Zebra Technologies\link_os_sdk\PC\v2.9.2275\lib"

 

I do not know if the error is my code or isn´t it possible to connect to my printer for incompatible with the SDK, Can anyone help me please?

 

On the other hand is possible print with the PrintService of JAVA  code, example:

 

FileInputStream inputStream = inputStream = new FileInputStream("C:/Temp/ticket.txt");

DocFlavor docFormat = DocFlavor.INPUT_STREAM.AUTOSENSE;

Doc document = new SimpleDoc(inputStream, docFormat, null);

PrintRequestAttributeSet attributeSet = new HashPrintRequestAttributeSet();

PrintService defaultPrintService = PrintServiceLookup.lookupDefaultPrintService();

if (defaultPrintService != null) {

String print_default = defaultPrintService.getName();

DocPrintJob printJob = defaultPrintService.createPrintJob();

try {

  printJob.print(document, attributeSet);

} catch (Exception er) {

  log.error("Error al imprimir: " + er.getMessage());

}

}