2006020311023827665.java

Create a time protocol over Client/Server Environment by sending request about time to server from c

package socket.timeprotocol;

import socket.timeprotocol.*;
import java.io.*;
import java.net.*;
import java.util.*;

//A network time server supporting RFC-868 over TCP.

public class TimeProtocolServer extends thread{
       //The TCP server socket used to receive connection requests
       protected ServerSocket server = null;
       //used to   control terminatin of the accept thread
       protected boolean isActive = true;
       //Server socket timeout milliseconds
       protected int socketTimeoutMillis = 5000;
       
       //Construct a new time protocol server:
       public TimeProtocolServer() throws SecurityException, IOException{
                        this(TimeProtocolConstants.TCP_PORT);
       }        //use the default port;
       
       //Constructs a new time server bound to the specified port
       public TimeProtocolServer(int port) throws SecurityException, IOException{
                        server = new ServerSocket(port);
                        server.setSoTimeout(socketTimeoutMillis);
                        start();
       }
       
       //Logs an error to System.err
       public void error(String message, Throwable e){
                System.err.println(new Date()+": TimeProtocolServer("
                                       +server.getLoacalPort()+"): error:"
                                       +message+": "+e.getClass().getName()+": "
                                       +e.getMessage());
       }
       
       //Logs an information message to System.out
       public void info(String message){
                System.out.println(new Date()+": TimeProtocolServer("
                +server.getLocalPort()+"):info: "+message);
       }
       
       //Requests asynchronous termination of the server
       public void terminate(){
                isActive = fase;
       }
       
       //Processes a new connection.  Typically in a separate thread but since 
       //we don't read from the client and comp is trivial, processing can be 
       //perfomed in the same thread.
       protected void process(Socket socket){
                if(socket == null){
                        return;
                }
                try{
                   info("Connection from "+socket.getInetAddress().getHostName()
                                    +":"+socket.getPort());
                   BufferedOutputStream bos = 
                                new BufferedOutputStream(socket.getOutputStream(),socket.getSendBufferSize());
                                
                   //number of seconds since January 1, 1900 0:0:0:0 UTC
                   long resultSecs = ((System.currentTimeMillis()+TimeProtocolConstants.EPOCH_OFFSET_MILLIS)/1000);
                   bos.write((int)((resultSecs >> 24) & 0xFF));
                   bos.write((int)((resultSecs >> 16) & 0xFF));
                   bos.write((int)((resultSecs >> 8) & 0xFF));
                   bos.write((int)(resultSecs & 0xFF));
                   bos.close();          //very important; needed to flush stream contents
                }catch(java.io.IOException){
                        error("I/O Error", e);
                }
                finally{
                       	try{
                       	    socket.close();
                       	}catch(IOException e){
                       	    error("Error closing socket",e);
                       	}
               }
        }
        
         //Server socket accept thread; loops until termination
         public void run(){
                info("Accepting connections on TCP port "
                                +server.getLocalPort()+"...");
                while(isActive){
                        Socket socket = null;
                        try{
                            socket = server.accept();
                            process(socket);
                        }catch(java.io.InterruptedIOException e){
                                //Used to periodically check for termination
                        }catch(IOException e){
                                error("I/O Error",e);
                        }catch(SecurityException e){
                                error("Unauthorized client attemptting to connect",e);
                        }catch(Throwable e){
                                error("Unexpected exception",e);
                        }
                }
                
                try{
                    server.close();
                }catch(IOException e){
                        error("Error closing server socket",e);
                } 
                info("server thread terminated");
        }
        
        //Prints usage to System.err and exits with error code 1
        public static void usageExit(){
                System.err.println("Usage: TimeProtocolServer {<port>}");
                System.exit(1);
        }

        //create a time protocol server. Invocation accepts a single optional port number.
        public static void main(String[] args){
                //Parse command-line arguments
                int port = 0;
                if(args.length == 0){
                        port = TimeProtocolConstants.TCP_PORT;
                }
                else if(args.length == 1){
                        try{
                            port = Integer.parseInt(args[0]);
                        }catch(NumberFormatException e){usageExit();}
                }else{usageExit();}
                
                //Start time protocols server
                TimeProtocolServer server = null;
                try{
                    server = new Time ProtocolServer(port);
                }catch(java.net.BindException e){
                        System.err.println("The server could not bind to port"+port
                        +"(may already be used): "+e.getMessage());
                        if(port <1024){
                                System.err.println("Warning: On user-level"
                                +"processes cannot bind to ports below 1024");
                        }
                }catch(java.io.IOException e){
                                System.err.println(e.getMessage());
                }catch(SecurityException e){
                                System.err.println("Permission to bind to port"+port 
                                +" denied(check security policy): "+e.getMessage());
                }
                if(server == null){
                        System.exit(1);
                }
                try{
                        server.join();
                }catch(InterruptedException e){
                        System.err.println("Errorwhile joined to server thead: "+e.getMessage());
                        System.exit(1);
                }
        }
}