FileZilla Server 升级到V0.9.39后开启服务出现：FTP over TLS is not enabled, users cannot securely 提示的解决办法！
FileZilla Server 0.9.39升级后, 进入管理面板, 会出现如下警告提示: You appear to be behind a NAT router. Please configure the passive mode settings and forward a range of ports in your router. Warning: FTP over TLS is not enable...