I came across Socket.IO.
It seems to be a service for creating, amongst other things, messaging and chat apps.
What I want to know is:
Is sending messages via Socket free? Or do I need to have my own server? For example PubNub allows you to send messages through its own servers but charges you for it (you have a small free allowance for beginners).
Taifun has created an extension for PubNub. Can Kodular use Socket.IO as it is or will an extension be necessary?