Is there a link or address where I can test a valid connection to photon?

What i mean by this is that, on some internet connections like WiFi, a certain address might be blocked. For example an office WiFi will give free access to a Google page or any other work related page but might restrict a Facebook or an online game address like Clash of Clans.

I would like to know so that I can give the user an appropriate response like "Internet Connection Restricted" or something like that.