I have had an instance recently were our webserver (host website and app api) turned its toes up and the redundancy did not kick in.
This highlighted a vital missing element of our app which is missing. The App reported 'poor or missing connection' based on XMLHttpRequest.readyState = 0 when infact the server was offline.
Is there a viable method to report if a server is off line or the problem is client end (poor signal)?