Something to showcase socket IO usage in action.

• You start by creating an instance of Socket IO server, it can be connected to an http server you created like done here, or working on its own.
• Socket io is event driven so the flow is mainly driven by the on(eventName, handler) function, that simply handle and event with a given name, by a given function.
• And the most important event is the connection event that's where you
  • identify the client
  • Add them into a room
  • set the events of interest of that client to keep it updated with messages on those events that are meant for them.
• There is surely authentication in socket IO, its data is sent from the client and is accessible from handshake field of the socket. for security it's passed on the auth field inside it.
• We may add a middleware on a socket server using the use function, similar to express. except it takes socket, and next as inputs, but works intuitively enough as you'd expect, if not pay a visit for the docs.

• Similarly, you would create a socket io client that connects to the server providing the credentials in the options if required.
• Then the client would provide handler for the events its interested to listen on.
• The client can also send messages using the emit function (actually similarly can the server).