/*
 * @(#)TimeServer.java	1.3 01/12/13
 * Listen for connections and tell callers what time it is.  
 * Demonstrates NIO socket channels (accepting and writing), 
 * buffer handling, charsets, and regular expressions.
 *
 * 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 
 * FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, 
 * SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF 
 * THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN 
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that Software is not designed, licensed or 
 * intended for use in the design, construction, operation or 
 * maintenance of any nuclear facility. 
 */

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.util.*;
import java.util.regex.*;


public class TimeServer {

    // We can't use the normal daytime port (unless we're running as root,
    // which is unlikely), so we use this one instead
    private static int PORT = 8013;

    // The port we'll actually use
    private static int port = PORT;

    // Charset and encoder for US-ASCII
    private static Charset charset = Charset.forName("US-ASCII");
    private static CharsetEncoder encoder = charset.newEncoder();

    // Direct byte buffer for writing
    private static ByteBuffer dbuf = ByteBuffer.allocateDirect(1024);


    // Open and bind the server-socket channel
    //
    private static ServerSocketChannel setup() throws IOException {
	ServerSocketChannel ssc = ServerSocketChannel.open();
	InetSocketAddress isa
	    = new InetSocketAddress(InetAddress.getLocalHost(), port);
	ssc.socket().bind(isa);
	return ssc;
    }

    // Service the next request to come in on the given channel
    //
    private static void serve(ServerSocketChannel ssc) throws IOException {
	SocketChannel sc = ssc.accept();
	try {
	    String now = new Date().toString();
	    sc.write(encoder.encode(CharBuffer.wrap(now + "\r\n")));
	    System.out.println(sc.socket().getInetAddress() + " : " + now);
	    sc.close();
	} finally {
	    // Make sure we close the channel (and hence the socket)
	    sc.close();
	}
    }

    public static void main(String[] args) throws IOException {
	if (args.length > 1) {
	    System.err.println("Usage: java TimeServer [port]");
	    return;
	}

	// If the first argument is a string of digits then we take that
	// to be the port number
	if ((args.length == 1) && Pattern.matches("[0-9]+", args[0]))
	    port = Integer.parseInt(args[0]);

	ServerSocketChannel ssc = setup();
	for (;;)
	    serve(ssc);

    }

}