How access Linux guest localhost from Mac's host?

Briefly, how from a Mac host's browser can I access a localhost server in a Linux guest -- without otherwise exposing that guest's localhost to the outside world?

In more detail...

I'm running Parallels Desktop 13 for Mac Pro Edition under macOS High Sierra (10.13.3). In Parallels I have an Ubuntu Linux 16.04 guest.

In that Linux guest, I have a website that I can access from a browser within the guest, at a localhost address.

How can I access that same website from a browser in the host Mac?

 

I realize that I had partially figured this out, with help, on an earlier occasion. In my Mac host's /etc/hosts file, either I had to add a line of the form

10.211.55.xx ubuntu-linux.shared ubuntu-linux #prl_hostonly shared

or else that was done automatically during installation of the Linux guest. And then I had to just use that IP address in the Mac host's browser, i.e. something of the form:

http://10.211.55.xx/website_name

But is the guest's website protected from the outside world (to the extent that my non-server Mac is protected from the outside world)?

 

Can we have more informations about this ? Maybe things changed with 16 version