Rules engine examples

I am really liking zerotier but finding the rules engine very confusing. It seems like there has been a lot of thought put into it, I feel it would benefit from a growing list of examples, beginner stuff, stuff that can be built upon.

For example, I have two nodes. Node A and Node B → How can I restrict Node A to only be able to access Node B on one particular port?

Seems simple and i’m sure the answer is a one liner but having some simple examples would go a long way for people coming into this, myself included. Having such a great mesh/distributed network is great but being able to manage that securely is where most of us fail.