From Project HungerGames.

BungeeUtils

package fr.skyost.bungeegames.utils;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.EventListener;
import java.util.HashMap;
import java.util.List;
import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.messaging.Messenger;
import org.bukkit.plugin.messaging.PluginMessageListener;
import org.bukkit.plugin.messaging.PluginMessageRecipient;

public class BungeeUtils implements PluginMessageListener {
	
	private final String subChannel;
	private final Plugin plugin;
	private final BungeeMessagesListener listener;
	
	public enum MessageType {
		CONNECT("Connect"),
		CONNECT_OTHER("ConnectOther"),
		IP("IP"),
		PLAYER_COUNT("PlayerCount"),
		PLAYER_LIST("PlayerList"),
		GET_SERVERS("GetServers"),
		MESSAGE("Message"),
		GET_SERVER("GetServer"),
		FORWARD("Forward"),
		UUID("UUID"),
		UUID_OTHER("UUIDOther");
		
		public final String name;
		private final static HashMap<String, MessageType> BY_NAME = new HashMap<String, MessageType>();
		
		MessageType(final String name) {
			this.name = name;
		}
		
		public static final MessageType fromName(final String name) {
			 return BY_NAME.get(name);
		}
		
	    static {
	        for(final MessageType type : values()) {
	        	BY_NAME.put(type.name, type);
	        }
	    }
	}
	
	public BungeeUtils(final Plugin plugin, final String subChannel) {
		final Messenger messenger = Bukkit.getMessenger();
		messenger.registerOutgoingPluginChannel(plugin, "BungeeCord");
		messenger.registerIncomingPluginChannel(plugin, "BungeeCord", this);
		this.subChannel = subChannel;
		this.plugin = plugin;
		listener = (BungeeMessagesListener)plugin;
	}
	
	public interface BungeeMessagesListener extends EventListener {
		void onMessageReceived(final MessageType type, final String[] response);
	}
	
	@Override
	public final void onPluginMessageReceived(final String channel, final Player player, final byte[] message) {
		try {
			if(!channel.equals("BungeeCord")) {
				return;
			}
			final DataInputStream in = new DataInputStream(new ByteArrayInputStream(message));
			final String typeStr = in.readUTF();
			MessageType type = MessageType.fromName(typeStr);
			final List<String> response = new ArrayList<String>();
			if(type == null) {
				type = MessageType.FORWARD;
				if(typeStr.equals(subChannel)) {
					for(final String line : in.readUTF().split(" ")) {
						response.add(line);
					}
				}
			}
			else {
				switch(type) {
				case IP:
				case PLAYER_COUNT:
					response.add(in.readUTF());
					response.add(String.valueOf(in.readInt()));
					break;
				case PLAYER_LIST:
				case UUID_OTHER:
					response.add(in.readUTF());
					response.add(in.readUTF());
					break;
				case GET_SERVERS:
				case GET_SERVER:
				case UUID:
					response.add(in.readUTF());
					break;
				default:
					break;
				}
			}
			listener.onMessageReceived(type, response.size() == 0 ? new String[]{"Nothing"} : response.toArray(new String[response.size()]));
		}
		catch(Exception ex) {
			ex.printStackTrace();
		}
	}
	
	public final void sendRequest(final MessageType type, final String server, final String destPlayer, final String arg, final String subChannel) throws IOException {
		sendRequest(type, server, destPlayer, arg, subChannel, Bukkit.getOnlinePlayers()[0]);
	}
	
	public final void sendRequest(final MessageType type, final String server, final String destPlayer, final String arg, final String subChannel, final PluginMessageRecipient sender) throws IOException {
		final ByteArrayOutputStream b = new ByteArrayOutputStream();
		final DataOutputStream out = new DataOutputStream(b);
		out.writeUTF(type.name);
		switch(type) {
		case CONNECT:
		case PLAYER_COUNT:
		case PLAYER_LIST:
			out.writeUTF(server);
			break;
		case CONNECT_OTHER:
			out.writeUTF(destPlayer);
			out.writeUTF(server);
			break;
		case MESSAGE:
			out.writeUTF(destPlayer);
			out.writeUTF(arg);
			break;
		case FORWARD:
			final byte[] data = arg.getBytes();
			out.writeUTF(server);
			out.writeUTF(subChannel);
			out.writeShort(data.length);
			out.write(data);
			break;
		case UUID_OTHER:
			out.writeUTF(destPlayer);
			break;
		default:
			break;
		}
		sender.sendPluginMessage(plugin, "BungeeCord", b.toByteArray());
	}
	
}

Sympa ta classe ;)