/**
  * 向目标(broker)发送一条stomp命令
  * @param BigpipeFrame $cmd
  * @return true on success or false on failure
  */
 public function send($cmd)
 {
     $buff_size = $cmd->store();
     if (0 == $buff_size) {
         BigpipeLog::warning("[_request package error][%s]", $cmd->last_error_message());
         return false;
     }
     return $this->_connection->send($cmd->buffer(), $buff_size);
 }