UDP Client and Server

The UDP client and server are created with the help of DatagramSocket and Datagram packet classes. If the UDP protocol is used at transport, then the unit of data at the transport layer is called a datagram and and not a segment. In UDP, no connection is established. It is the responsibility of an application to encapsulate data in datagrams (using Datagram classes) before sending it. If TCP is used for sending data, then the data is written directly to the socket (client or server) and reaches there as a connection exists between them. The datagram sent by the application using UDP may or may not reach the UDP receiver.

UDP client

import java.io.*; import java.net.*;

public class MyUDPClient
{
public static void main(String[] args) { try { // InetAddress class is used to getting local address InetAddress ia = InetAddress.getLocalHost(); //DatagramSocket class is used creating UDP socket DatagramSocket ds=new DatagramSocket(1236,ia); // this is message string passes to the server String y="Hell srver i am client"; //converting this string in to byte array with help of getBytes() method byte [] b=y.getBytes(); //creating DatagramPacket of byte array DatagramPacket dp =new DatagramPacket(b,b.length,ia,8); // send to the server socket ds.send(dp); System.out.println("sending String :"+(new String(b))); //b1 is a byte array is created because its use in DatagramPacket byte[] b1=new byte[50]; //now the DatagramPacket object is created with byte array DatagramPacket in = new DatagramPacket(b1,b1.length); //recieve() method of datagram socket objectis used to recive data from put in the byte array ds.receive(in); System.out.println("message from server :"+(new String(b1))); //closing the connection ds.close(); } catch(SocketException se) { System.out.println(se); } catch(Exception e) { System.out.println(e); } }
}

UDP Server code

import java.io.*; import java.net.*;

public class MyUDPServer { public static void main(String[] args) { try{ //creating a UDP socket(datagramsocket) class object where 8 is port number DatagramSocket ds=new DatagramSocket(8); //b1 is a byte array is created because its use in DatagramPacket byte[] b1=new byte[50]; //now the DatagramPacket object is created with byte array DatagramPacket in = new DatagramPacket(b1,b1.length); //recieve() method of datagram socket objectis used to recive data from put in the byte array ds.receive(in); System.out.println("recieving String :"+(new String(b1))); String y="Hello client i am server"; byte [] b=y.getBytes(); DatagramPacket out =new DatagramPacket(b,b.length,in.getAddress(),in.getPort()); // send method of DatagramPacket is used to sending the data to client socket ds.send(out); ds.close(); } catch(SocketException se) { System.out.println(se); } catch(Exception e) { System.out.println(e); } }
}

OUTPUT

First run the server program; than you can see it wait for client addresses.

Now run the client program; then you will get the following output.

The server will show the message sent by the client.