I used an skey https://en.wikipedia.org/wiki/S/KEY port sequence and had a small java app that would run upon my humble Nokia and Psion Organiser to provide the port sequence for that minute in time.
Not sure I have the code about still alas, due to that system getting lost along with others in a move a decade ago, but was simple enough to craft together and worked well.
Even had a http/s tarpit, which is highly recommended educational wise to do and insightful.
Again it is security with obscurity, just a bit more obfuscation involved in this type of set-up.
Oh and dynamic DNS so home IP was known as was dynamic IP allocation via the ISP.
I used an skey https://en.wikipedia.org/wiki/S/KEY port sequence and had a small java app that would run upon my humble Nokia and Psion Organiser to provide the port sequence for that minute in time.
Not sure I have the code about still alas, due to that system getting lost along with others in a move a decade ago, but was simple enough to craft together and worked well. Even had a http/s tarpit, which is highly recommended educational wise to do and insightful.
Again it is security with obscurity, just a bit more obfuscation involved in this type of set-up.
Oh and dynamic DNS so home IP was known as was dynamic IP allocation via the ISP.