Bom Acho que não á nescessidades de explicação, como nome diz, ant dualbox, ou seja ativado somente 1 box por player ingame

Código:
package: net.sf.l2j.gameserver.model.customs - create ant dual box.java

/* 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 2, 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., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 *
 * http://www.gnu.org/copyleft/gpl.html
 */
package net.sf.l2j.gameserver.model.custom;

import net.sf.l2j.gameserver.ThreadPoolManager;
import net.sf.l2j.gameserver.clientpackets.Say2;
import net.sf.l2j.gameserver.model.L2World;
import net.sf.l2j.gameserver.model.actor.instance.L2PcInstance;
import net.sf.l2j.gameserver.serverpackets.CreatureSay;

/**
 * 
 * @author xAddytzu
 */
public class 
ProtectionNetwork
{
   public static void disc(final L2PcInstance player)
   {
      player.sendPacket(new CreatureSay(1, Say2.HERO_VOICE, "SYSTEM", "You cannot play with dualbox."));
      ThreadPoolManager.getInstance().scheduleGeneral(new Runnable()
      {
         public void run()
         {
            player.closeNetConnection();
         }
      }, 20000);
   }
   public static boolean check(L2PcInstance player)
   {
      boolean loggedz0r = false;
      for (L2PcInstance playerz0r : L2World.getInstance().getAllPlayers())
      {
         String client = first(playerz0r);
         String client1 = second(player);
         if (client.equalsIgnoreCase(client1));
            loggedz0r = true;
      }
      return loggedz0r;
   }
   private static String first(L2PcInstance player)
   {
      return second(player).toString();
   }
   private static String second(L2PcInstance player)
   {
      try
      {
         return player.getClient().getConnection().getSocketChannel().socket().getInetAddress().getHostAddress();
      } catch (Throwable t){}
      return null;
   }
}

Index: java/net/sf/l2j/gameserver/clientpackets/EnterWorld.java
===================================================================
--- java/net/sf/l2j/gameserver/clientpackets/EnterWorld.java	(revision 130)
+++ java/net/sf/l2j/gameserver/clientpackets/EnterWorld.java	(working copy)
@@ -105,6 +105,11 @@
 			getClient().closeNow();
 		    return;
 		}
+		
+      if (activeChar.Player())

+               if (ProtectionDualBox.check(activeChar))
+          			{
+   					activeChar.sendMessage("[Ant-DualBOX]: You can not use Dual-Box because that server is blocked.!");
+          			}
+                   	ProtectionDualBox.disc(activeChar);
Creditos: xAddytzu