The RTCEF_SESSION_REFERRED event is fired when the RTC Client API receives a request (an appropriate SIP REFER message) on a connected session to transfer the call to a different endpoint.
On receiving this event, the application can either create a new call to the transfer target by calling IRTCSessionReferredEvent::Accept on the event or stay connected in the existing call and reject the transfer by calling IRTCSessionReferredEvent::Reject on the event interface.