@Override
    public Promise<Integer> playerCount(String serverName) {
        Promise<Integer> fut = Promise.empty();
        sendMessage(new PlayerCountAgent(serverName, fut));
        return fut;
    }
Sends (or queues the sending of) the message encapsulated by the given message agent

@param agent the agent
helper/src/main/java/me/lucko/helper/messaging/bungee/BungeeCordImpl.java