Question is the web service part, where real-time communication should happen.
What, exactly, is the question?
(I'm assuming that you don't actually mean real-time
, as that would be impossible over a mobile or even Wifi network -which I'm assuming you're talking about since you posted this in the Android forum.)
If the client is a native app you could use notifications like Google's FCM
. If, OTOH, you mean a web client, then in addition to web sockets you might want to look into Server-sent events
. Both are supported in current versions of Firefox and Chrome for Android.