Add plugin channel support for plugins.

api/src/main/java/net/md_5/bungee/api/ProxyServer.java

@@ -152,4 +152,26 @@ public abstract class ProxyServer
      * instance to fail to boot
      */
     public abstract void start() throws Exception;
+
+    /**
+     * Register a channel for use with plugin messages. This is required by some
+     * server / client implementations.
+     *
+     * @param channel the channel to register
+     */
+    public abstract void registerChannel(String channel);
+
+    /**
+     * Unregister a previously registered channel.
+     *
+     * @param channel the channel to unregister
+     */
+    public abstract void unregisterChannel(String channel);
+
+    /**
+     * Get an immutable set of all registered plugin channels.
+     *
+     * @return registered plugin channels
+     */
+    public abstract Collection<String> getChannels();
 }

proxy/src/main/java/net/md_5/bungee/BungeeCord.java

@@ -7,6 +7,7 @@ import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.Socket;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -20,6 +21,7 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 import lombok.Getter;
 import lombok.Setter;
+import lombok.Synchronized;
 import static net.md_5.bungee.Logger.$;
 import net.md_5.bungee.api.ProxyServer;
 import net.md_5.bungee.api.ReconnectHandler;
@@ -34,6 +36,7 @@ import net.md_5.bungee.api.plugin.PluginManager;
 import net.md_5.bungee.command.*;
 import net.md_5.bungee.config.YamlConfig;
 import net.md_5.bungee.packet.DefinedPacket;
+import net.md_5.bungee.packet.PacketFAPluginMessage;
 
 /**
  * Main BungeeCord proxy class.
@@ -73,7 +76,6 @@ public class BungeeCord extends ProxyServer
      * Fully qualified connections.
      */
     public Map<String, UserConnection> connections = new ConcurrentHashMap<>();
-    public Map<String, List<UserConnection>> connectionsByServer = new ConcurrentHashMap<>();
     /**
      * Tab list handler
      */
@@ -91,6 +93,7 @@ public class BungeeCord extends ProxyServer
     @Getter
     @Setter
     private ConfigurationAdapter configurationAdapter = new YamlConfig();
+    private final Collection<String> pluginChannels = new HashSet<>();
 
 
     {
@@ -272,8 +275,8 @@ public class BungeeCord extends ProxyServer
     @Override
     public Server getServer(String name)
     {
-        List<UserConnection> users = connectionsByServer.get(name);
+        Collection<ProxiedPlayer> users = getServers().get(name).getPlayers();
-        return (users != null && !users.isEmpty()) ? users.get(0).getServer() : null;
+        return (users != null && !users.isEmpty()) ? users.iterator().next().getServer() : null;
     }
 
     @Override
@@ -281,4 +284,37 @@ public class BungeeCord extends ProxyServer
     {
         return config.getServers();
     }
+
+    @Override
+    @Synchronized("pluginChannels")
+    public void registerChannel(String channel)
+    {
+        pluginChannels.add(channel);
+    }
+
+    @Override
+    @Synchronized("pluginChannels")
+    public void unregisterChannel(String channel)
+    {
+        pluginChannels.remove(channel);
+    }
+
+    @Override
+    @Synchronized("pluginChannels")
+    public Collection<String> getChannels()
+    {
+        return Collections.unmodifiableCollection(pluginChannels);
+    }
+
+    public PacketFAPluginMessage registerChannels()
+    {
+        StringBuilder sb = new StringBuilder();
+        for (String s : getChannels())
+        {
+            sb.append(s);
+            sb.append('\00');
+        }
+        byte[] payload = sb.substring(0, sb.length() - 1).getBytes();
+        return new PacketFAPluginMessage("REGISTER", payload);
+    }
 }

proxy/src/main/java/net/md_5/bungee/ServerConnection.java

@@ -89,6 +89,9 @@ public class ServerConnection extends GenericConnection implements Server
             ServerConnection server = new ServerConnection(socket, info, in, out, login);
             ServerConnectedEvent event = new ServerConnectedEvent(user, server);
             ProxyServer.getInstance().getPluginManager().callEvent(event);
+
+            out.write(BungeeCord.getInstance().registerChannels().getPacket());
+
             return server;
         } catch (KickException ex)
         {

proxy/src/main/java/net/md_5/bungee/UserConnection.java

@@ -103,6 +103,8 @@ public class UserConnection extends GenericConnection implements ProxiedPlayer
                 clientEntityId = newServer.loginPacket.entityId;
                 serverEntityId = newServer.loginPacket.entityId;
                 out.write(newServer.loginPacket.getPacket());
+                out.write(BungeeCord.getInstance().registerChannels().getPacket());
+
                 upBridge = new UpstreamBridge();
                 upBridge.start();
             } else