public void leaveChannel(string channelName)
{
Entity entity = new Entity ();
entity.id = "chatjoin";
LeaveChat leaveChat = new LeaveChat ();
ChatChannel chatChannel = new ChatChannel ();
chatChannel.name = channelName;
leaveChat.chatChannel.Add (chatChannel);
entity.leaveChat = leaveChat;
actorSystem.FindRemote ("default").Tell (entity);
subscribers.Remove (channelName);
}