Contains a common API for the XllRtdFeed RTD server, for calls from the RTD server to XLL clients.
IXllRtdFeedCallback is the abstract base class that handles events raised by the XllRtdFeed RTD server. A class that is derived from IXllRtdFeedCallback must implement two virtual functions: OnGetDataState() and OnTopicRemoved().
An XLL that uses the XllRtdFeed RTD server must create an instance of a class derived from IXllRtdFeedCallback, and pass a pointer to the instance using CXllRtdFeedServerProxy::RegisterClient().
During initialization (usually OnXllOpenEx()), a client should create an instance of a class that implements IXllRtdFeedCallback, and pass it to the RTD server via CXllRtdFeedServerProxy::RegisterClient().
The instance should be removed during termination (usually OnXllClose()) with CXllRtdFeedServerProxy::UnregisterClient().