Here you can find the source of getKey()
private static byte[] getKey() throws SocketException
//package com.java2s; /**/*from w ww . j a v a 2 s . co m*/ * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 3 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. * */ import java.net.NetworkInterface; import java.net.SocketException; import java.util.Arrays; import java.util.Enumeration; public class Main { private static byte[] getKey() throws SocketException { Enumeration<NetworkInterface> ni = java.net.NetworkInterface.getNetworkInterfaces(); if (ni.hasMoreElements()) { byte[] mac = ni.nextElement().getHardwareAddress(); if (mac != null) { return Arrays.copyOf(mac, 8); } else { return "aGorRiaA".getBytes(); } } else { return "aGorRiaA".getBytes(); } } }