/*
 * @(#)LAN.java 1.1 2003/04/24
 *
 */

import java.net.*;
import java.util.*;

/**
 * Have a machine Wake-on-LAN
 * Sends the magic sequence in an UDP datagram to a machine.
 * The magic sequence is 6 0xFF followed by the machine's ethernet address
 * repeated at least 16 times.
 * 
 * @author Michael John Wensley 
 * @author Mads Bahrt
 * @version 2003/04/24
 */
public class LAN {
    public static void main(String args[]) throws java.io.IOException {
        if (args.length >= 2) {
            InetAddress ia = InetAddress.getByName(args[0]);
            byte[] eth = ethernet(args[1]);
            System.out.print("Sending ");

            String s;
            for(int i = 0; i < eth.length; i++) {
                s = Integer.toHexString(eth[i]);
                while(s.length() < 2)
                    s = "0" + s;

                System.out.print(s.substring(s.length() - 2));
                if (i < (eth.length -1)){
                System.out.print("-");
                }
            }
            System.out.println(" to " + ia.getHostAddress());
        
            wake(ia, eth);
            
            System.out.println("Sent");
        }
        else{
        System.out.println("Wake-on-lan for Java");
        System.out.println("Written by Michael John Wensley and slightly modified by Mads Bahrt.");
        System.out.println("Usage:java LAN ipaddress|domainname macaddress");
        System.out.println("Example: java LAN 192.168.1.2 00-50-BA-D1-A4-95");
        System.out.println("or: java LAN someone.mydomain.tld 00-50-BA-D1-A4-95");
        }
        //System.in.read(); // Optional - wait for a keypress before exiting
    }
    /**
     * Send magic packet to a computer
     * @param ipaddr The machine's Internet Protocol address.
     * @param ethernet The machine's Ethernet address.
     */
    private static void wake(InetAddress ipaddr, byte[] ethernet) throws java.io.IOException {
        byte[] magic = new byte[6 + 16 * ethernet.length];
        
        for (int i=0; i < 6; i++)
            magic[i] = (byte)0xff;

        for (int i = 6; i < magic.length; i += ethernet.length)
            System.arraycopy(ethernet, 0, magic, i, ethernet.length);

        // send it to the discard port, 9 so that the machines TCP stack will discard it.
        // we could send it to the echo port, 7, so that the machine returns the packet,
        // if it is already online. Could also ping the machine with the magic sequence as data.
        DatagramPacket gram = new DatagramPacket(magic, magic.length, ipaddr, 9);
        new DatagramSocket().send(gram);
    }
    /**
     * Parse an ethernet address string into its bytes.
     * @param address The address as hexadecimal represented bytes separated with '-'
     * @return The address as a byte array.
     */
    private static byte[] ethernet(String address) {
        StringTokenizer parts = new StringTokenizer(address, "-");

        byte[] ab = new byte[parts.countTokens()];
        for(int i=0; i < ab.length; i++)
            ab[i] = (byte)Integer.parseInt(parts.nextToken(), 16);

        return ab;
    }
}