provides an example of peer to peer communication

[OlegDokuka]

closes #867

[rstoyanchev]

PeerToPeerCommunicationExample is very general. Something a little more specific for the use case perhaps like TaskProcessingServerWithNotificationsExample or similar.

For the package, we currently have the duplex package which also shows a server-to-client interaction although a very basic one. Perhaps we can add this sample to the same package and give the package a better name like clientresponder or servertoclient. The word duplex to me is a little ambiguous (since a channel interaction is also duplex) and not as clear as it could be.

[rstoyanchev]

A class-level Javadoc with an overview of the idea behind the sample would be very useful. For example based on the #867 (comment):

Example of a long-running process that handles tasks (a.k.a Kafka style) where a
client submits tasks via fireAndForget and then receives notifications also via
fireAndForget from the server side.

In the example, the client sends some tasks initially, then disappears, then connects
again and receives undelivered that have completed in the mean time.

[rstoyanchev]

Maybe this can be consolidated into the background process which already polls and sends fireAndForget. That would simplify the TasksAcceptor significantly and perhaps it could be even inlined at the point of creating the server.

As a consequence it might take up to 2 seconds for the client to catch up but that seems okay. Also server-to-client notifications could delivered as a list (or comama-separated String) perhaps, i.e. as a batch rather than one at a time.

[OlegDokuka]

I moved it to a separate method now

[OlegDokuka]

@rstoyanchev duplex is less obvious. I stands for renaming it to p2p since it is more familiar to everyone. Duplex can easily be mixed with a channel which kind of duplex channel communication