function onMessage(ProcConnection $conn, $data) {
        if ($this->_status == self::STATUS_INIT)
            return;
        $data = self::_parseTex($data);
        if ($data === false)
            return;
        if ($this->_status == self::STATUS_FORMULA) {
            $this->_formula = $data;
            $this->_id = self::genPic($data);
            $this->_status = self::STATUS_RESULT;
            $conn->send($this->_current->withEval());
        } else {
            $message = $this->_current->getMessage();
            msg_send(Captcha::getQueue(), 1, [$this->_id, $message, $data]);
            if (msg_stat_queue(Captcha::getQueue())['msg_qnum'] < Config::get('CAPTCHA_CACHE_MAX')) {
                $this->generate();
            } else {
                $this->_status = self::STATUS_INIT;
            }
        }
    }