5 rt_thread4.1.0版本，使用EC200S，开启NTP后，显示超时

        if (sendto_ntp_server(sockfd, host_name_buf[i], &serv_addr[server_num]) > 0)
        {
            server_num ++;
                          rt_thread_mdelay(500); /* 此处加500ms延时，防止出现AT发送与接收碰撞 */
        }
    }    

int get_ec200s_link_status(void)
{
#ifdef PKG_USING_AT_DEVICE
    /* "ec200x" 名字来源于设备注册时使用的名字，在文件 packages/at_device-v2.0.4/samples/at_sample_ec200x.c 中定义 */
    struct at_device * ec200x_dev = at_device_get_by_name(AT_DEVICE_NAMETYPE_NETDEV, "ec200x");
    if (ec200x_dev == RT_NULL)
    {
        LOG_E("func: %s. get ec200x at device failed", __FUNCTION__);
        return -1;
    }
    if (ec200x_dev->is_init == RT_FALSE)
    {
        LOG_E("%s is not init", "ec200x");
        return -1;
    }
    if (netdev_is_up(ec200x_dev->netdev) == 0)
    {
        return -1;
    }
    if (netdev_is_internet_up(ec200x_dev->netdev))
    {
        return 0;
    }
    else
    {
        return -1;
    }
#else
    return -1;
#endif
}