counterserver1.java

JAVA分布式程序学习的课件（全英文）

import java.io.*;

/**
 * This module contains the application logic of a Counter server
 * which uses a  datagram socket for interprocess communication.
 * A command-line argument is required to specify the server port.
 * @author M. L. Liu
 */
public class CounterServer1 {

   /* state information */
   static int counter = 0;

   public static void main(String[] args) {
      int serverPort = 12345;    // default port
      if (args.length == 1 )
         serverPort = Integer.parseInt(args[0]);       
      try {
         // instantiates a datagram socket for both sending
         // and receiving data
   	   MyServerDatagramSocket mySocket = 
            new MyServerDatagramSocket(serverPort); 
/**/     System.out.println("Counter server ready.");  
         while (true) {  // forever loop
            DatagramMessage request = 
               mySocket.receiveMessageAndSender();
            System.out.println("Request received");
            // The message received is unimportant; it is the sender's
            // address that we need in order to reply.
			   // Now increment the counter, then send its value to the client.
            increment( );
/**/        System.out.println("counter sent: "+ counter);
            // Now send the reply to the requestor
            mySocket.sendMessage(request.getAddress( ),
               request.getPort( ), String.valueOf(counter));
		   } //end while
       } // end try
	    catch (Exception ex) {
          ex.printStackTrace( );
	    }
   } //end main

   static private synchronized void increment( ){
       counter++;    
   }
 
} // end class