Протокол UDP

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];
         DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
         serverSocket.receive(receivePacket);
         String sentence = new String( receivePacket.getData(), 0, receivePacket.getLength());
         System.out.println("RECEIVED BYTES: " + receivePacket.getLength());
         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);
         System.out.print("Press enter to finish");
         System.in.read();
      }
}

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[] receiveData = new byte[1024];
      String sentence = inFromUser.readLine();
      byte[] sendData = new byte[sentence.length()];
      sendData = sentence.getBytes();
      System.out.println("Length:" + sentence.length());
 
      DatagramPacket sendPacket = new DatagramPacket(sendData, sentence.length(), IPAddress, 9876);
      clientSocket.send(sendPacket);
      DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
      clientSocket.receive(receivePacket);
      String modifiedSentence = new String(receivePacket.getData(), 0, receivePacket.getLength());
      System.out.println("FROM SERVER:" + modifiedSentence);
      clientSocket.close();
      System.out.print("Press enter to finish");
      System.in.read();
   }
}

import java.io.*;
import java.net.*;
 
public class UDPClient {
    
    private static String[] data = {"We", "never", "thought", "it", "was", "the", "end"};
    private DatagramSocket clientSocket;
    InetAddress addr;
    DatagramPacket packet;
    
    public static void main(String[] args)
    {
        UDPClient client = new UDPClient();
        client.send();
        
    }
    
    public UDPClient()
    {
        try
        {
            clientSocket = new DatagramSocket();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
    
    protected void send()
    {
        try
        {
            addr = InetAddress.getByName("localhost");
            for (String s : data)
            {
                byte[] byteArray = s.getBytes();
                packet = new DatagramPacket(byteArray, byteArray.length, addr, 2005);
                clientSocket.send(packet);
            }
            
            System.out.println("Datagram sent");
            clientSocket.close();
            
        } catch (Exception e)
        {
            e.printStackTrace();
        }
    }
    
}

import java.io.*;
import java.net.*;
 
public class UDPServer {
    
    public static final int PORT = 2005;
    private DatagramSocket servSocket;
    private boolean keepRunning = true;
    String output;
    
    public static void main(String[] args) {
        
        UDPServer server = new UDPServer();
        server.service();
   }
    
    public UDPServer()
    {
        try
        {
            servSocket = new DatagramSocket(PORT);
            
        }
        catch(SocketException e)
        {
            System.err.println("Unable to open socket : " + e.toString());
        }   
    }
    
    protected void service() {
        
        DatagramPacket datagram;
        byte[] data;
      
        while (keepRunning)
        {
            try {
                data = new byte[7];
                datagram = new DatagramPacket(data, data.length);
                servSocket.receive(datagram);
            
                output = new String(data,  0, datagram.getLength());
                System.out.print(output + " ");
            
                if (output.equals("end")) 
                {
                    keepRunning = false;
                    System.out.println("\nDatagram received");
                }
            
            
            } catch(IOException e) {
             
                System.err.println("I/O Exception : " + e.toString());
            }
        }
        servSocket.close();
    }
}