Where can I find a rough list of requirements and technology stack for advanced web chat?

Question

Computer networks

Actually the question: I want to write a text web chat. The inputs are as follows:
Architecture: client-server. TCP protocol.
Language (not relevant to the question, but I'll clarify just in case) - python
What is now ready: There is a server and client script - clients can exchange messages with each other. In principle - the basic and main part is ready - the chat does exactly what it should, BUT I want to somehow (yes, exact wording)) develop its functionality - not in the sense of emoticons and other rubbish (especially since so far - that this is just a console text chat), but to increase fault tolerance, add support for some specialized protocols, encryption? The problem is that I can't figure out where to develop this whole thing - and it all ends with the above formulations - "some protocols, etc." For example, Telegram, Viber and the like - can you see somewhere an approximate stack of technologies / "chips" that are implemented in them?
What can you advise to develop the idea?

Answer 1

Take an open protocol and screw it up. For example XMPP.

Answer 2

The transport protocol is websocket and optionally webrtc (for data transfer between clients, for example, files to transfer or an audio / video call)
Choose the encryption yourself, and this is not a python but a javascript client side.
Fault tolerance is not a bit about choosing a protocol, but about organizing a backend in principle. Plus testing in various situations.
For example, mobile networks often ban webrtc (generally a capricious protocol, so consider a fallback to the classic transmission through the server) plus the fight against nat, server stun, etc.
Text chat is a very simple task, you can stupidly look at the examples for websocket and webrtc, all the nuances just come out when you start adding features.