i've a problem with my codes, when ever i run it, i got an error from the checking i implemented. Can some pls explain why does the error keep coming.

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

public class EchoClient{
 static final int serverPort = 1026;
 static final int packetSize = 1024;
public static void main(String args[]) throws  UnknownHostException, SocketException{
 DatagramSocket socket; //How we send packets
 DatagramPacket packet; //what we send it in
 InetAddress address; //Where to send
 String messageSend; //Message to be send
 String messageReturn; //What we get back  from the Server
 byte[] data;
 //Checks for the arguments that sent to  the java interpreter
 // Make sure command line parameters correctr
 if(args.length != 2)
 System.out.println("Usage Error : Java EchoClient < Server name> < Message>");
 // Gets the IP address of the Server
 address = InetAddress.getByName(args[0]);
 socket = new DatagramSocket();
 data = new byte[packetSize];
 messageSend = new String(args[1]);
 messageSend.getBytes (0,messageSend.length(),data,0);
// messageSend.getBytes(0, messageSend.length(), data, 0);            
 // remember datagrams hold bytes
 packet = new DatagramPacket(data,data.length,address,serverPort);
 System.out.println(" Trying to Send the packet ");
  // sends the packet
  catch(IOException ie)
  System.out.println("Could not Send :"+ie.getMessage());
  //packet is reinitialized to use it for recieving
  packet = new DatagramPacket(data,data.length);
  // Receives the packet from the server
  catch(IOException iee)
  System.out.println("Could not receive :  "+iee.getMessage() );
  // display message received
  messageReturn = new String (packet.getData(),0);
  System.out.println("Message Returned : "+
  }    // main
 } // Class EchoClient

Exactly what error do you get from which statement?

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at EchoClient.main(EchoClient.java:33)
from line 22.

Based on what you have posted, EchoClient.java:33 is
messageSend = new String(args[1]);
which cannot generate the exception you describe, so please post the code that corresponds to the error message.