how to Receive UDP packets, when it comes from server? for android java

Question

I have used a thread for UDP receive packet. When I am sending a packet to that particular IP, where the UDP receive program runs. The application will be stopped unfortunately. Then if I remove the thread called new Thread(new Runnable()) and public void run the application will run good, but only one data has received. My intention is to receive data at the receiver end continuously, when data comes. please acknowledge me.

udpserver.java:

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;


public class UdpServer extends Activity {
/** Called when the activity is first created. */
private TextView data;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    data = (TextView) findViewById(R.id.textView);

        runUdpServer();

}
private static final int UDP_SERVER_PORT = 11111;
private static final int MAX_UDP_DATAGRAM_LEN = 1500;
private void runUdpServer() {
    new Thread(new Runnable() {
        public void run() {
            String lText;
            byte[] lMsg = new byte[MAX_UDP_DATAGRAM_LEN];
            DatagramPacket dp = new DatagramPacket(lMsg, lMsg.length);
            DatagramSocket ds=null;
            try {
                 ds = new DatagramSocket(UDP_SERVER_PORT);
                //disable timeout for testing
                //ds.setSoTimeout(100000);
                ds.receive(dp);
                lText = new String(dp.getData());
                Log.i("UDP packet received", lText);
                data.setText(lText);
            } catch (SocketException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            finally {
                if (ds != null) {
                    ds.close();
                }
            }
        }
    }).start();
}

Solution

This is a working snippet I am using to receive and parse UDP packets.

  try {
        int port = 11000;

        DatagramSocket dsocket = new DatagramSocket(port);
        byte[] buffer = new byte[2048];
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

        while (true) {

            dsocket.receive(packet);
            lText = new String(buffer, 0, packet.getLength());
            Log.i("UDP packet received", lText);
            data.setText(lText);

            packet.setLength(buffer.length);
        }
    } catch (Exception e) {
        System.err.println(e);
        e.printStackTrace();
    }

Comments

[user207421]

You're ignoring the length in the datagram.

[user207421]

You're ignoring the length in the datagram.

[jobcrazy]

@EJP Yes, more details about buffer size or even timeout issue should be considered, but this answer only give a work sample to fix the continuous read issue.

[Dinesh Anton Raja]

the above solutions are not sufficient..only one time the packet has received..but i need the solution that, whenever the packet comes, it has to receive the packet

[Dinesh Anton Raja]

please acknowledge me for continuos packet reception..if once socket is closed, then it will not be re-assigned.after closing of socket only i can see the incoming data..

[jobcrazy]

@DineshAntonRaja you mean you want to recreate the socket and continue to receive packet when exception throws?

[Dinesh Anton Raja]

@jobcrazy i need to read the packet whenever it comes. But now only one time the packet has received. i think no exception throws...i have attached the code in the following website. (www.pdaraja.weebly.com).... i have tired the while loop(true). my intention is the program should always ready to receive the packet. please acknowledge me

[Dinesh Anton Raja]

pdaraja.weebly.com/uploads/1/8/2/3/18237947/udpserver.txt this is the code i have used..

[jobcrazy]

You should not close it until exception throws, just remove ds.close();

[Dinesh Anton Raja]

can you please send me the code. because if i remove ds.close() it will not show the output in textview. then i am using while(true), so how can i code. please acknowledge me..

[Dinesh Anton Raja]

@jobcrazy can you please send me the code. because if i remove ds.close() it will not show the output in textview. then i am using while(true), so how can i code. please acknowledge me.

[jobcrazy]

@DineshAntonRaja check your code carefully plz, use !ds.isClosed() not ds.isClosed() in your while loop