When a message is sent from the protocol stack to the application, it is sent in an ISDN_PACKET structure. This ISDN_PACKET structure is contained in the buffer element of the data structure returned by the function ctaWaitEvent.
For more information about receiving ISDN messages, see Network access identifiers (NAIs).
ISDN_PACKET is defined as follows:
typedef struct ISDN_PACKET
{
ISDN_MESSAGE message; /* ISDN message identification information */
BYTE data[4]; /* Data included in packet (>=0) */
} ISDN_PACKET;