# Receiving SIP events

All messages and events from the SIP server are returned to the application through the standard NaturalAccess event handling mechanism, along with standard NaturalAccess events and any events specific to NaturalAccess extensions. The SIP events are always NCC events that arrive in the CTA_EVENT data structure. For more information about NaturalAccess events, refer to the Dialogic® NaturalAccess™ Software Developer’s Manual.

All events from... | Are prefixed with...
NCC API | NCCEVN_
ADI API | ADIEVN_
NaturalAccess | CTAEVN_

To receive these events, a NaturalAccess application can invoke ctaWaitEvent.

Some call-control-related NaturalAccess events are unsolicited. They can occur at any time, regardless of the application's current activities. Usually, unsolicited events indicate that something has happened on the trunk or in the session.

The eventmask parameter, which dictates whether certain informational call control events are generated, is found in the NCC_START_PARMS structure. For more information, refer to the Dialogic® NaturalAccess™ NaturalCallControl™ API Developer’s Manual.