DenySpout.java

package com.md_5;

public class DenySpout extends org.bukkit.plugin.java.JavaPlugin implements org.bukkit.event.Listener {

    @Override
    public void onEnable() {
        try {
            Class<?>[] params = {int.class, boolean.class, boolean.class, Class.class};
            java.lang.reflect.Method addClassMapping = net.minecraft.server.Packet.class.getDeclaredMethod("a", params);
            addClassMapping.setAccessible(true);
            addClassMapping.invoke(null, 195, true, true, CustomPacket.class);
        } catch (Exception ex) {
        }
        getServer().getPluginManager().registerEvents(this, this);
    }

    @org.bukkit.event.EventHandler
    public void onJoin(org.bukkit.event.player.PlayerJoinEvent event) {
        net.minecraft.server.Packet18ArmAnimation packet = new net.minecraft.server.Packet18ArmAnimation();
        packet.a = -42;
        ((org.bukkit.craftbukkit.entity.CraftPlayer) event.getPlayer()).getHandle().netServerHandler.sendPacket(packet);
    }

    public static class CustomPacket extends net.minecraft.server.Packet {

        public CustomPacket() {
        }

        public int a() {
            return 8;
        }

        public void a(java.io.DataInputStream in) throws java.io.IOException {
            in.readShort();
            in.readShort();
            in.skipBytes(in.readInt());
        }

        public void a(java.io.DataOutputStream out) throws java.io.IOException {
        }

        public void handle(net.minecraft.server.NetHandler handler) {
            ((net.minecraft.server.NetServerHandler) handler).disconnect("Please use the orginal Minecraft client from www.minecraft.net");
        }
    }
}