I have asked before, without getting a definitive reply, so I need to ask again.
On page http://docs.vanillaforums.com/features/sso/ there is the line
jsConnect pings your endpoint whenever it wants to know if a user is logged in on your site. It does this using the user's current session, so you can use your normal "is logged in" detection to determine this - nothing fancy here.
I assume that jsConnect is putting "something" in a variable, and firing that at my endpoint. But what is it sending me, and assuming that it is a variable, what is the variable called? When it says, "user's current session", what is it referring to? Surely not $_SESSION? Possibly a cookie?
I have tried debugging the call as it comes into to my non-standard CMS, but can't see any pattern.