cc_ReleaseCall( )

Description | Cautions | Example | Errors | See Also

Name:	int cc_ReleaseCall(crn)
Inputs:	CRN crn	call reference number
Returns:	0 on success < 0 on failure
Includes:	cclib.h
Category:	Call control
Mode:	synchronous
Technology:	BRI/2; BRI/SC; PRI (all protocols)

Description

The cc_ReleaseCall( ) function instructs the driver and firmware to release all internal resources for the specified call. An inbound call will be rejected after cc_DropCall( ) is used. Every issue of cc_DropCall( ) must be followed by cc_ReleaseCall( ).

When cc_WaitCall( ) is used in synchronous mode and cc_ReleaseCall( ) is issued subsequently, the next inbound call on the same channel will be pending until the cc_WaitCall( ) function is issued again. If cc_WaitCall( ) is used in asynchronous mode, the inbound call notification can be received immediately after cc_ReleaseCall( ).

Parameter	Description
crn:	The call reference number. Each call needs a CRN.

Cautions

• Windows only: For new applications, it is recommended that the cc_ReleaseCallEx( ) function be used instead of the cc_ReleaseCall( ) function. Under load conditions, or if the remote end delays transmitting the RELEASE COMPLETE message, an application could experience a significant delay while the cc_ReleaseCall( ) function unblocks and returns control to the application. This delay can be up to 8 seconds long if the RELEASE COMPLETE message is never returned. The cc_ReleaseCall( ) function is supported only in synchronous mode; therefore, this problem occurs only in applications that use the asynchronous single-threaded programming model. In this case, when this blocking function is called within a handler processing the CCEV_DROPCALL event, it could create a bottleneck for processing any other event and, thereby, could affect call handling performance.
• After a connection is terminated, the cc_ReleaseCall( ) function should be called to release the call reference number (CRN). Failure to call this function may cause a blocking condition or a memory allocation error. Channels will remain allocated if call-related resources are not released.
• After the cc_ReleaseCall( ) function is issued, the CRN is no longer valid.

Example

#include <windows.h>   /* For Windows applications only */  
#include <stdio.h>  
#include <errno.h>  
#include "srllib.h"  
#include "dtilib.h"  
#include "cclib.h"  
void main()  
{  
   LINEDEV   devhdl    = 0;  
   CRN       crn = 0;  
   char     *devname = "dtiB1T1";  
   if ( cc_Open( &devhdl, devname, 0 ) < 0 )   
   {  
        printf("Error opening device: errno = %d\n", errno);  
        exit(1);  
   }  
   printf("Waiting for call\n");  
   if ( cc_WaitCall(devhdl, &crn, NULL, -1, EV_SYNC) < 0 )  
        procdevfail(devhdl);  
   if ( cc_AnswerCall(crn, 0, EV_SYNC) < 0 )  
        callfail(crn);  
        .  
        .  
        .  
        .  
        .  
   /* Drop the call with NORMAL CLEARING cause value */  
   if ( cc_DropCall(crn, NORMAL_CLEARING, EV_SYNC) < 0 )  
        callfail(crn);  
   if ( cc_ReleaseCall(crn) < 0 )  
        callfail(crn);  
   if ( cc_Close( devhdl ) < 0 )   
      printf("Error closing device, errno = %d\n", errno);  
}  
int callfail(CRN crn)  
{                 
        LINEDEV ld;  
         cc_CRN2LineDev(crn,&ld);  
         procdevfail(ld);  
}  
int procdevfail(LINEDEV handle)  
{  
        int reason;  
        char *msg;  
        reason = cc_CauseValue(handle);  
        cc_ResultMsg(handle,reason,&msg);  
        printf("reason = %x - %s\n",reason,msg);  
}

Errors

If the function returns < 0 to indicate failure, use the cc_CauseValue( ) function to retrieve the reason code for the failure. The cc_ResultMsg( ) function can be used to interpret the reason code. Error codes are defined in the files ccerr.h, isdnerr.h, and isdncmd.h.

Error codes from the cc_ReleaseCall( ) function include the following:

Error Code	Description
ERR_ISDN_LIB | E_ISBADIF	Bad interface number
ERR_ISDN_LIB | E_ISBADCALLID	Bad call identifier
ERR_ISDN_LIB | E_ISBADTS	Bad time slot
ERR_ISDN_LIB | E_ISNULLPTR	Null pointer error

See Also

• cc_AnswerCall( )
• cc_MakeCall( )
• cc_WaitCall( )
• cc_DropCall( )
• cc_ReleaseCallEx( )

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