I try to send a UDP packet from my mobile to a PC – IP 192.168.1.113, at the PC I use “Packet sender”with UDP server port 55777. But it does not work, I have sent UDP packet from a VBA script in Excel to the Packet sender and it works, I can also send through UDP apps I have downloaded to the mobile, to the “Packet sender”.
I use:
Android Studio 3.5
SDK platform 8.1
Mobile: Samsung S9+  
I have added the INTERNET permission to the manifest:
I send the packet from a new thread since the main thread does not allow to send packages, the below code is the first step before I continue, need to make this to work first though.
public class MainActivity extends AppCompatActivity {
    private Handler mainHandler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void startThread(View view) {
        ExampleRunnable runnable = new ExampleRunnable(10);
        new Thread(runnable).start();
    }
    class ExampleRunnable implements Runnable {
        @Override
        public void run() {
            DatagramSocket ds = null;
            String message = "Hello";
            try{
                ds = new DatagramSocket();
                InetAddress serverAddr = InetAddress.getByName("192.168.1.113");
                DatagramPacket dp;
                dp = new DatagramPacket(message.getBytes(), message.length(), serverAddr, 55777);
                ds.send(dp);
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (ds != null) {
                    ds.close();
                }
            }
        }
    }
}
 
     
    