I am unable to discover my zebra printer in the same subnet based on the java code but if I provide the list of IP address then I am able to discover it. Below I am adding the code that I used to discover the device.
 
import java.util.ArrayList;
import java.util.List;
 
 
import com.zebra.sdk.printer.discovery.DiscoveredPrinter;
import com.zebra.sdk.printer.discovery.DiscoveryException;
import com.zebra.sdk.printer.discovery.DiscoveryHandler;
import com.zebra.sdk.printer.discovery.NetworkDiscoverer;
 
 
/**
*
*
*/
public class NetworkCardDiscovererExample {
    public static void main(String[] args) {
        List printersToFind = new ArrayList();
        printersToFind.add("aaa.aaa.aaa.aaa");
        DiscoveryHandler discoveryhandler = new DiscoveryHandler() {
            List printers = new ArrayList();
 
 
            @Override
            public void foundPrinter(DiscoveredPrinter printer) {
                // TODO Auto-generated method stub
                System.out.print("Adding printer" + printer);
                printers.add(printer);
            }
 
 
            @Override
            public void discoveryFinished() {
                // TODO Auto-generated method stub0
                for (DiscoveredPrinter printer : printers) {
                    System.out.println(printer);
                }
                System.out.println("Discovered " + printers.size() + " printers.");
            }
 
 
            @Override
            public void discoveryError(String message) {
                // TODO Auto-generated method stub
                System.out.println("An error occured during discovery : " + message);
            }
        };
        try {
 
 
            int timeout = 3000;
 
 
            List ipList = new ArrayList();
 
 
            ipList.add("aaa.aaa.aaa.aaa");
 
 
            System.out.println("Starting printer discovery.");
 
 
            NetworkDiscoverer.findPrinters(discoveryhandler, ipList, timeout);
 
 
        } catch (DiscoveryException e) {
 
 
            e.printStackTrace();
 
 
        }
    }
}
 
In the above code it's not possible to discover if I remove the iplist.