timequery.java

jdk-6u10-docs java开发宝典

/*
 * @(#)TimeQuery.java	1.2 01/12/13
 * Ask a list of hosts what time it is.  Demonstrates NIO socket channels
 * (connection and reading), 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 
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 */

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


public class TimeQuery {

    // The standard daytime port
    private static int DAYTIME_PORT = 13;

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

    // Charset and decoder for US-ASCII
    private static Charset charset = Charset.forName("US-ASCII");
    private static CharsetDecoder decoder = charset.newDecoder();

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

    // Ask the given host what time it is
    //
    private static void query(String host) throws IOException {
	InetSocketAddress isa
	    = new InetSocketAddress(InetAddress.getByName(host), port);
	SocketChannel sc = null;

	try {

	    // Connect
	    sc = SocketChannel.open();
	    sc.connect(isa);

	    // Read the time from the remote host.  For simplicity we assume
	    // that the time comes back to us in a single packet, so that we
	    // only need to read once.
	    dbuf.clear();
	    sc.read(dbuf);

	    // Print the remote address and the received time
	    dbuf.flip();
	    CharBuffer cb = decoder.decode(dbuf);
	    System.out.print(isa + " : " + cb);

	} finally {
	    // Make sure we close the channel (and hence the socket)
	    if (sc != null)
		sc.close();
	}
    }

    public static void main(String[] args) {
	if (args.length < 1) {
	    System.err.println("Usage: java TimeQuery [port] host...");
	    return;
	}
	int firstArg = 0;

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

	for (int i = firstArg; i < args.length; i++) {
	    String host = args[i];
	    try {
		query(host);
	    } catch (IOException x) {
		System.err.println(host + ": " + x);
	    }
	}
    }

}