Not liking the solution you have doesn't mean you don't have a solution.
Anyway, watch the playlist I sent, it's a great overview of the OSI model with some other stuff. You mentioned not understanding some layers, once you do you will understand the limitations of the hardware you have.
You are basically asking for people to solve a solved problem, there's no actual need for keeping the PCs separate since you control them both, and oh and you want it done cheap. A bespoke custom solution will not scale regardless if you need it to or not, you should know that.
Tell them to fuck off, like I did a couple months ago.
Or tell them, you can go tell the customer they have a credit, because they made a mistake on the PO, or I will. Like I said a while ago.
Same job been there 6 years.
Ask your customer when they need it implemented by, because you don't have a timeline for it. Is this a software feature that can be added to the existing devices? Send the quote, set realistic expectations.
If you fall on a sword for your customer, they might have a place for you while you look for something permanent. Or a reference for something good.
Not liking the solution you have doesn't mean you don't have a solution.
Anyway, watch the playlist I sent, it's a great overview of the OSI model with some other stuff. You mentioned not understanding some layers, once you do you will understand the limitations of the hardware you have.