Java UDP Network Codes

Sending/Receiving Datagram Packets via UDP
The following are related to sending and receiving datagram packets via UDP.
1.DatagramPacket
2.DatagramSocket

DatagramPacket represents a datagram packet. Datagram packets are used for connectionless delivery and
normally include destination address and port information. DatagramSocket is a socket used for sending
and receiving datagram packets over a network via UDP. A DatagramPacket is sent from a DatagramSocketby
calling the send(...) method of DatagramSocket with DatagramPacket as the argument:
send(DatagramPacket dp). receive(DatagramPacket dp) is use for receiving aDatagramPacket.
(The MulticastSocket class may be used for sending/receiving aDatagramPacket to a mulitcast group. It is
a subclass of DatagramSocket that adds functionality for multicasting.)

UDP SERVER PROGRAM

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

class UDPServer
{
public static void main(String args[]) throws Exception
{
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while(true)
{
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String( receivePacket.getData());
System.out.println("RECEIVED: " + sentence);
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
}
}
}

UDP CLIENT PROGRAM


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

class UDPClient
{
public static void main(String args[]) throws Exception
{
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence = new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}
}