Gateway与bussinessWorker的通讯协议

问题描述

这里写问题描述
为什么打包的时候，head设置了固定了28个字节，没有设置更大或是更小，请问有什么用意吗

/**
     * 获取整个包的 buffer
     *
     * @param mixed $data
     * @return string
     */
    public static function encode($data)
    {
        $flag = (int)is_scalar($data['body']);
        if (!$flag) {
            $data['body'] = serialize($data['body']);
        }
        $data['flag'] |= $flag;
        $ext_len      = strlen($data['ext_data']);
        $package_len  = self::HEAD_LEN + $ext_len + strlen($data['body']);
        return pack("NCNnNnNCnN", $package_len,
            $data['cmd'], $data['local_ip'],
            $data['local_port'], $data['client_ip'],
            $data['client_port'], $data['connection_id'],
            $data['flag'], $data['gateway_port'],
            $ext_len) . $data['ext_data'] . $data['body'];
    }