Java by API/java.net/DatagramSocket

DatagramSocket: receive(DatagramPacket packet)

/*
 * Output:
 *  
 */
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class MainClass {
  private final static int BUFSIZE = 20;
  public static void main(String args[]) {
    try {
      int port = 80;
      DatagramSocket ds = new DatagramSocket(port);
      while (true) {
        byte buffer[] = new byte[BUFSIZE];
        DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
        ds.receive(dp);
        String str = new String(dp.getData());
        System.out.println(str);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

DatagramSocket: send(DatagramPacket p)

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import javax.swing.JPanel;
public class MainClass extends JPanel {
  public static void main(String[] args) {
    try {
      String data = "data in UDP";
      byte [] buffer = data.getBytes();
      DatagramPacket packet = new DatagramPacket(buffer, buffer.length,
                new InetSocketAddress("localhost", 5002));
      DatagramSocket socket = new DatagramSocket(5003);
      System.out.println("Sending a packet...");
      socket.send(packet);
    }catch(IOException e)
    {
      e.printStackTrace();
    }
  }
}

new DatagramSocket()

/*
 * Output:
 *  
 */
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class MainClass {
  public static void main(String args[]) {
    try {
      InetAddress ia = InetAddress.getByName("www.jexp.ru");
      DatagramSocket ds = new DatagramSocket();
      byte buffer[] = "hello".getBytes();
      DatagramPacket dp = new DatagramPacket(buffer, buffer.length, ia, 80);
      // Send the datagram packet
      ds.send(dp);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

new DatagramSocket(int port)

/*
 * Output:
 *  
 */
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class MainClass {
  private final static int BUFSIZE = 20;
  public static void main(String args[]) {
    try {
      int port = 80;
      DatagramSocket ds = new DatagramSocket(port);
      while (true) {
        byte buffer[] = new byte[BUFSIZE];
        DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
        ds.receive(dp);
        String str = new String(dp.getData());
        System.out.println(str);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}