Hi all. Long time draytek user but need a bit of help.
Ok, I have a Samsung smart tv, connected to my network but specifically connected to my NAS.
Now, its wired cat 5.
I want to BLOCK the tv from connecting any further than my network, so it has no outside access but want it to be able to access my files on my NAS.

I suppose this could apply to lots of devices, printers, for example, that are known to "phone home".
So I figure you would need to know the protocol and port(s) used which is the first obstacle. I've looked at wireshark briefly but, well, tbh its a few levels more advanced than my networking skills.
Although I have set up my router with RDP and numerous SSIDs, some of which are isolated. What I'm trying to say my skills are "intermediate novice".
Then have to program the router using the information.
So, could anyone suggest how to start to accomplish this?
Thank you.

Vigor 2820 but when this fails, next router will be a draytek. Make my life easier having a familiar interface structure.

You don't need to block ports, just the IP address. The firewall rules won't block any internal LAN traffic so you just need a rule which blocks the TV's IP address. Ensure the TV gets a fixed IP address either by the router's bind-ip FHCP facility or by hardsetting it on the TV itself.

Thank you.
Ok, my next question is obvious. There seems to be a great many firewall options, such as blocking port forwarding and blocking websites and creating objects.
Would you possibly mind elaborating a bit? It seems it should be a simple thing but I'm genuinely struggling to accomplish this.

You just need one firewall rule which blocks source x.x.x.x (your TV's IP address). Setting it up isn't simple, there are knowledgebase articles to help.