You don't write code to do the srtp that's handled by the browser, you actually often use websockets to signal, but basically you could write a socket.io node or golang server then use one of google's free stun services and do realtime video chat with just that without the need for a specialized webrtc server. If you're building a robust product you would want to add in coturn to authenticate the media layer rather than using google's free stun server.