/*
 * @(#)NBTimeServer.java	1.4 01/12/13
 * A non blocking Internet time server implemented using
 * the New I/O (NIO) facilities added to J2SE v 1.4.
 *
 * Copyright 2001-2002 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
 * conditions are met:
 * 
 * -Redistributions of source code must retain the above copyright  
 * notice, this  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduct the above copyright 
 * notice, this list of conditions and the following disclaimer in 
 * the documentation and/or other materials provided with the 
 * distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY 
 * EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY 
 * DAMAGES OR LIABILITIES  SUFFERED BY LICENSEE AS A RESULT OF  OR 
 * RELATING TO USE, MODIFICATION OR DISTRIBUTION OF THE SOFTWARE OR 
 * ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE 
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 * SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF 
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 * 
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 */

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.channels.spi.*;
import java.net.*;
import java.util.*;

// Listen on a port for connections and write back the current time.
public class NBTimeServer {
    private static final int DEFAULT_TIME_PORT = 8900;

    // Constructor with no arguments creates a time server on default port.
    public NBTimeServer() throws Exception {
	acceptConnections(this.DEFAULT_TIME_PORT);
    }

    // Constructor with port argument creates a time server on specified port.
    public NBTimeServer(int port) throws Exception {
	acceptConnections(port);
    }

    // Accept connections for current time. Lazy Exception thrown.
    private static void acceptConnections(int port) throws Exception {
	// Selector for incoming time requests
	Selector acceptSelector = SelectorProvider.provider().openSelector();

	// Create a new server socket and set to non blocking mode
	ServerSocketChannel ssc = ServerSocketChannel.open();
	ssc.configureBlocking(false);

	// Bind the server socket to the local host and port

	InetAddress lh = InetAddress.getLocalHost();
	InetSocketAddress isa = new InetSocketAddress(lh, port);
	ssc.socket().bind(isa);
	
	// Register accepts on the server socket with the selector. This
	// step tells the selector that the socket wants to be put on the
	// ready list when accept operations occur, so allowing multiplexed
	// non-blocking I/O to take place.
	SelectionKey acceptKey = ssc.register(acceptSelector, 
					      SelectionKey.OP_ACCEPT);
	
	int keysAdded = 0;
	
	// Here's where everything happens. The select method will
	// return when any operations registered above have occurred, the
	// thread has been interrupted, etc.
	while ((keysAdded = acceptSelector.select()) > 0) {
	    // Someone is ready for I/O, get the ready keys
	    Set readyKeys = acceptSelector.selectedKeys();
	    Iterator i = readyKeys.iterator();

	    // Walk through the ready keys collection and process date requests.
	    while (i.hasNext()) {
		SelectionKey sk = (SelectionKey)i.next();
		i.remove();
		// The key indexes into the selector so you
		// can retrieve the socket that's ready for I/O
		ServerSocketChannel nextReady = 
		    (ServerSocketChannel)sk.channel();
		// Accept the date request and send back the date string
		Socket s = nextReady.accept().socket();
		// Write the current time to the socket
                PrintWriter out = new PrintWriter(s.getOutputStream(), true);
		Date now = new Date();
		out.println(now);
		out.close();
	    }
	}
    }

    // Entry point.
    public static void main(String[] args) {
	// Parse command line arguments and
	// create a new time server (no arguments yet)
	try {
		NBTimeServer nbt = new NBTimeServer();
	} catch(Exception e) {
		e.printStackTrace();		
	}
    }
}
