IMO the easiest path is to use a ready-made chat SDK and a hosted service. But it only make sense if their pricing fit your business model. Usually such servi

IMO the easiest path is to use a ready-made chat SDK and a hosted service. But it only make sense if their pricing fit your business model. Usually such services are priced by number of users and/or concurrent connections. So they only make sense when you're small and very fast can become prohibitively expensive. Then it's a time to implement your own messaging functionality.