1.7.8. Retrieve Information for a GLOBAL or NULL CRN Event

The GCIS_EXID_GETNONCALLMSG extension ID retrieves information for a GLOBAL or NULL CRN event, at the time the event occurs. The GCIS_EXID_GETNONCALLMSG extension ID must be used immediately after the event is received if the application needs the call information. The library will not queue the call information; subsequent messages on the same board device will overwrite this information if it is not retrieved immediately. NULL events correspond to messages received with a dummy, or NULL, call reference value (CRV). These messages are of significance to all calls or channels on a particular trunk, that is, they do not correspond to a particular call. Therefore, the messages are delivered on the board level device (for example, briS1). This extension ID can be used to retrieve information for the following NULL events:

• GCEV_EXTENSION with ext_id as GCIS_EXEV_INFONULL
• GCEV_EXTENSION with ext_id as GCIS_EXEV_NOTIFYNULL
• GCEV_EXTENSION with ext_id as GCIS_EXEV_FACILITYNULL

GLOBAL events correspond to messages received with a Zero call reference value. These messages are of significance to all calls or channels on a particular trunk, that is, they do not correspond to a particular call. Therefore, the messages are delivered on the board level device (for example, briS1). This extension ID can be used to retrieve the information for the following GLOBAL events:

• GCEV_EXTENSION with ext_id as GCIS_EXEV_INFOGLOBAL
• GCEV_EXTENSION with ext_id as GCIS_EXEV_NOTIFYGLOBAL
• GCEV_EXTENSION with ext_id as GCIS_EXEV_FACILITYGLOBAL

Note: Some IEs may require a Call Reference Value (CRV) to be part of the contents. The Call Reference, in this case, must be the Call Reference value assigned by the network, not the Call Reference Number (CRN) that is generated by GlobalCall and retrieved using the gc_GetCRN( ) function. It is up to the application to correctly format and order the IEs. Refer to the ISDN Recommendation Q.931 or the switch specification of the application's ISDN protocol for the relevant CCITT format. See the example code for details. To receive GLOBAL and NULL events, an appropriate handler must be enabled on the board level device (see the sr_enbhdlr( ) function in the System Runtime Library Programmer's Guide).

The information related to a GLOBAL or NULL event must be retrieved immediately as it will be overwritten by the next event.

The following table provides the parameter inputs for the gc_Extension( ) function.

Parameter	Input
target_type	GCTGT_GCLIB_CHAN
target_id	board device handle of the device
ext_id	GCIS_EXID_GETNONCALLMSG
retblkp	set_id - GCIS_SET_DLINK
	parm_id - GCIS_PARM_DLINK_CES
	values - 0 for PRI 1-8 for BRI when used as a network-side terminal.
	value_type - char
	parm_id - GCIS_PARM_DLINK_SAPI
	values - 0 for BRI and PRI 16 for X.25 packets over D-channel
	value_type - char
	set_id - GCIS_SET_IE
	parm_id - GCIS_PARM_IEDATA
	values - user provided
	value_type - char array, length should not exceed MAXLEN_IEDATA
mode	EV_SYNC

Example

 int extGetNonCallMsg (LINEDEV handle)
{
         GC_PARM_DATAP parm_datap;
         GC_PARM_BLKP parm_blkp = NULL, ret_blkp = NULL;
         unsigned long mode;
         int ret_val = 0;
         GC_INFO  t_Info;
         mode = EV_SYNC;
          ret_val = gc_Extension( GCTGT_GCLIB_CHAN, handle,
                         GCIS_EXID_GETNONCALLMSG, parm_blkp, &ret_blkp, mode);
          if ( ret_val )
         {
             ret_val = gc_ErrorInfo(&t_Info);
             if (ret_val == GC_SUCCESS) {
                    printf("gc_ErrorInfo() successfully called\n");
                    PrintGC_INFO(&t_Info);
            }         
         gc_util_delete_parm_blk( parm_blkp );
         gc_util_delete_parm_blk( ret_blkp );
         return ret_val;
}

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