The Server should never have to call functions on the Client side in order to process a request. The Client should always send enough information to the Server in its request so that the Server can process the request and send back a response without having to ask for more information from the Client.
Btw ... you should use the "SEARCH" option of this Forum to check if your question hasn't already been answered. For example, by searching for "Server calling" you will get the following two topics, closely related to your current question:
Streaming headlines...How to work TRtcDelayedCall?Also, to avoid generating large topics with a lot of unrelated questions in the RTC Forums, please start a new Topic for every question you have and try to shortly describe your question in the Topic subject line. I have split your last topic into two separate topics now to get a similar effect.
Best Regards,
Danijel Tkalcec