How to sign sockets?

Question

Node.js

I am developing a private anonymous chat with a random search for an interlocutor (1 on 1).
Stack used: nginx (as a proxy for the node), node.js, socket.io, angular (in the future).
Analogues have big problems with bots. Here I have a question with signing a message. Maybe I'm not using the term properly. I need the server to be sure that it receives messages from its client, and not from a written bot (after all, if you look at the client code, you can decrypt the entire socket system and write your own bot client). To protect against MitM, I'm going to tie SSL, though I don't know how yet (probably if I tie it to nginx, it will save me).
And so there was a question how to identify the client?

Answer 1

Well, the protection mechanism against bots in chats is not new - one-time tokens, various checks (user agent, whether JS / Flash is enabled, etc.) + captcha