Improved UDPClient.java

As per our in-class discussion on 2002-02-22, Kurose and Ross's UDPClient.java program can be improved in the following ways:

There is no reason to allocate an array of 1024 bytes to initialize sendData, because this array becomes garbage without ever being used.
Receiving a packet shouldn't hang forever; a timeout should be set. (Ideally the client should then retry the request, since it is idempotent. This isn't illustrated below.)
When the received data is converted into a String, not all 1024 bytes should be converted. Instead, the received packet's length should govern this.

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("max.mcs.gac.edu.");
        byte[] sendData;
        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.setSoTimeout(1000);
        clientSocket.receive(receivePacket);
        String modifiedSentence =
            new String(receivePacket.getData(), 0, receivePacket.getLength());
        System.out.println("FROM SERVER:" +
                           modifiedSentence);
        clientSocket.close();
    }
}