Sessions have nothing to do with communication or connections. In order to send a message to any Client, the Server needs an active connection with that Client and there has to be an active Rrequest from that Client waiting for a Response from the Server. In short, for the Server to be able to send anything to a Client, the Client has to send a request to the Server to ask for that information. The Server does not have the capability to open a connection to a Client, nor does the Server has the possibility to send a message to the Client without being asked for it explicitly by the Client.
Check the RTC_Messenger Demo to see how delayed calls can be used with RTC remote functions to implement a long polling mechanism, which makes it possible for the Clients to get an instant response from the Server if there is data waiting, or delay the response until there is data available for the Client.
You might also want to
check this topic from the RTC SDK FAQ Archive.
... and this
old Topic from the RTC SDK Support Archive:
Best Regards,
Danijel Tkalcec