code: public void ping(long id, long timeout, PingCallback callback) {
          pingCallbacks.put(id, callback);
          scheduller.postMessage(new MTPing(id), false, timeout);
          actionsActor.send(new PingTimeout(id), timeout);
      }
docs: Perform Ping
  
  @param id       ping id
  @param timeout  ping timeout
  @param callback ping callback