Independent of firewalls or other considerations, there are two basic ways gain access to a VirtualBox VM Guest hosting e.g. a web server.

The first option is to add a bridged network adapter (this is the simplest solution). This will add a virtual adapter for the Guest that can be accessed like any normal machine (i.e. via a discrete local IP address ex. assigned by your router's DHCP).

The second option is to use the existing NAT adapter's Advanced options to configure port forwarding, like you would on a router. That is, you would take e.g. port 80, and tell VirtualBox to pass requests for that port to your Guest.

Independent of firewalls or other considerations, there are two basic ways gain access to a VirtualBox VM Guest hosting e.g. a web server.

The first option is to add a bridged network adapter (this is the simplest solution). This will add a virtual adapter for the Guest that can be accessed like any normal machine on the network (i.e. via a discrete local IP address ex. assigned by your router's DHCP).

The second option is to use the existing NAT adapter's Advanced options to configure port forwarding, like you would on a router. That is, you would take e.g. port 80, and tell VirtualBox to pass requests for that port to your Guest.