I think before going into code, the terminology has to be sorted out.
Telnet is an (very outdated) internet communication protocol. JSON in contrast is a data-structure for composite objects. You could send data in json-structure over telnet, but now a days you will use the “Hyper-Text-Transport-Protocol” instead. This protocol is better known as HTTP and it is not limited to browsers.
Likewise, a “server” usually receives requests from a client and sends responses. So I assume you will not have a server on a computer, but a client. Instead the server will be on the Plasma2350W.
So the challenge for you is to code the server on the Plasma2350W and the client on the computer. The nice thing about the internet is that many people have already solved these kind of challenges and a simple search (like: pimoroni plasma server) indeed turns up many hits. I did not try any of those implementations, but this one seems well documented with good instructions (which is always a hint that the code might be good as well):