NP3

UPD
import java.io.*;
import java.net.*;
import java.util.*;
public class UDPEchoClient
{
private static InetAddress host;
private static final int PORT=1234;
private static DatagramSocket datagramSocket;
private static DatagramPacket inPacket,outPacket;
private static byte[] buffer;
public static void main(String[] args)
{
try{
host=InetAddress.getLocalHost();
}
catch(UnknownHostException u)
{
System.out.println("Host ID not found");
System.exit(1);
}
accessServer();
}
private static void accessServer()
{try{
datagramSocket=new DatagramSocket();
DataInputStream userEntry=new DataInputStream(System.in);
String message="",response="";
do{
System.out.println("Enter Message");
message=userEntry.readLine();
if(!message.equals("CLOSE"))
{
outPacket=new DatagramPacket(message.getBytes(),message.length(),host,PORT);
datagramSocket.send(outPacket);
buffer=new byte[256];
inPacket=new DatagramPacket(buffer,buffer.length);
datagramSocket.receive(inPacket);
response=new String(inPacket.getData(),0,inPacket.getLength());
System.out.println("\n"+response);
}
}while(!message.equals("CLOSE"));
}
catch(IOException ex)
{
ex.printStackTrace();
}
finally{
System.out.println("\nClosing Connection");
datagramSocket.close();
}
}
}

=================
import java.io.*;
import java.net.*;
public class UDPEchoServer
{
private static final int PORT=1234;
private static DatagramSocket datagramSocket;
private static DatagramPacket inPacket,outPacket;
private static byte[] buffer;
public static void main(String[] args)
{
System.out.println("Opening Port...\n");
try{
datagramSocket=new DatagramSocket(PORT);
}
catch(SocketException sockEx)
{
System.out.println("Unable to attach to port");
System.exit(1);
}
handleClient();
}
private static void handleClient()
{
try{
String messageIn,messageOut;
int numMessages=0;
do{
buffer =new byte[256];
inPacket=new DatagramPacket(buffer,buffer.length);
datagramSocket.receive(inPacket);
InetAddress clientAddress=inPacket.getAddress();
int clientPort=inPacket.getPort();
messageIn=new String(inPacket.getData(),0,inPacket.getLength());
System.out.println("Message Receives");
numMessages++;
messageOut="Message"+numMessages+":"+messageIn;
outPacket=new DatagramPacket(messageOut.getBytes(),messageOut.length(),clientAddress,clientPort);
datagramSocket.send(outPacket);
}while(true);
}
catch(IOException e)
{e.printStackTrace();
}
finally
{
System.out.println("\nClosing Connection..\n");
datagramSocket.close();
}
}
}