Connect to VirtualBox Guest Machine from Host OS with NAT Port Forwarding

Motivation

I want to connect to NameServers in Docker Containers,
and the Docker installed on Ubuntu 18.04,
and the Ubuntu 18.04 running in VirtualBox on my Windows Host OS,

... so this is required.

Simple Notes

Step 1: Right click on stopped (power off) machine, click "Settings..."

Step 2: Click Network -> Advanced -> Port Forwarding

Step 3: Click the add Sign, input Host Port and Guest Port, click OK

Now the request to localhost:9487 will be forwarded to the Guest Machine

Reference

How to Forward Ports to a Virtual Machine and Use It as a Server