Sending ISDN-specific messages

Not all variants support the sending and receiving of ISDN-specific messages. The capability mask lists the capabilities for each variant. The application determines whether a variant supports sending and receiving of ISDN messages by invoking nccQueryCapability. The NCC_CAP_SEND_CALL_MESSAGE bit in the capability mask returned by this function indicates if the variant supports this capability.

To send ISDN-specific messages, use nccSendCallMessage. nccSendCallMessage takes the following arguments:

Argument

Description

callhd

Call handle to which message should be sent.

message

Pointer to buffer containing the message structure.

size

Size of the buffer.

All ISDN-specific structures and macros associated with NCC are defined in nccxisdn.h. Each of the structures in this file contains:

The header structure is:

typedef struct 
{
    WORD message_id;              /* Message id                */
    WORD message_type;            /* Message type              */
} NCC_ISDN_SEND_CALL_MESSAGE;

message_id field values

The following table lists possible values for the message_id field:

message_id value

Description

NCC_ISDN_TRANSPARENT_BUFFER

Transparent message sending operation.

NCC_ISDN_TRANSFER_CALLID_RQ

Request a call identifier for a call to be transferred.

message_type field values

The following table lists possible values that can be returned in the message_type field:

message_type value

Description

NCC_ISDN_RETURN_REJECT

Rejection of a request to invoke the operation.

NCC_ISDN_RETURN_RESULT

Successful completion of the operation.

NCC_ISDN_RETURN_ERROR

Unsuccessful completion of the operation.

To invoke an operation, use any of NCC_ISDN_xxx_INVOKE structures, where xxx is the ID of the message. The structure to use depends upon what operation the application is to perform. For example, the structure used to invoke TBCT is NCC_ISDN_TBCT_INVOKE.