You seem to have missed out my favorite deepstream.io. It is an open source realtime server that supports both websockets and http. I've extensively worked with it and IMO it is one of easiest with all the realtime features like Pub/Sub, Data-sync, Presence, Realtime Search, RPCs etc being available.

Creating a realtime application would require the knowledge of the technologies, paradigms and protocols involved according to the use-case you are implementing for. However even after acquiring this knowledge, it's pretty complex to implement all of these from scratch yourself. The usual way would be to use one of the PaaS or IaaS services/APIs that are available out there like deepstream.io , pusher, socket.io , Firebase, etc. I've extensively used deepstream.io . It is an open source realtime server with both websockets and http support. Hence, IMO it would be a great option. They have a community that is responsive to any queries in case you get stuck somewhere while implementing it. Hope this helps.

With firebase, you could either use your own custom authentication logic or let the users use an anonymous authentication strategy with a possibility of later elevating the profile to an authenticated user. But if you do not wish to associate any kind of authentication with the users, you could use deepstream . It is completely open sourced and provides a no auth mechanism where any user who connects to your app can start using it without any authentication step.