EvmCallback(5)							File Formats Manual						    EvmCallback(5)

NAME

       EvmCallback() - event management (EVM) callback function

SYNOPSIS


DESCRIPTION

       An  EVM callback function is a function that you provide to allow your program to handle messages arriving on an EVM connection.  Most mes-
       sages are incoming events or responses to requests you have made to the EVM daemon, but you may also get a callback for other reasons.

       Specify the name (EventCB) of the callback function in the callback parameter when you create an EVM connection with  a	response  mode	of
       callback.

       Your callback function is invoked by which you must call whenever you detect activity pending on the connection.

       An EVM callback function must conform to the prototype shown.

   Callback Function Parameters
	 o  The  connection parameter contains the connection context pertaining to this callback.  This value was returned by when the connection
	    was created.  If you have one callback function servicing multiple connections, you might test this to determine  which  connection  a
	    particular invocation is handling.

	 o  The callbackArg parameter contains the value you specified as the callbackArg parameter to when you created the connection.  For exam-
	    ple, you might use it to hold a pointer to your own context data for the connection.

	 o  The callbackData parameter points to a structure containing the details of the callback.  The structure  includes  a  callback  reason
	    code, an event, and a union containing data specific to each possible reason.  The event member may contain NULL if it is not applica-
	    ble to the reason.	You may get these reasons:

	 This callback reason indicates that the daemon was unable to
		   deliver one or more events, probably because the client process had not finished processing earlier events, causing the connec-
		   tion buffer to overflow.

		   If necessary, you can use to increase the size of the receive buffer.  See the EvmConnControl(3) reference page.

	 This callback reason indicates that an EVM event has been received from
		   the	daemon.  The event is available in the structure.  You must use to free the event when you have finished with it.  See the
		   EvmEventDestroy(3) reference page.

	 This callback reason indicates that a prior
		   call has completed, usually with a response from the daemon if the responseMode was specified as when the connection  was  cre-
		   ated.  The posting status is available in the structure.

	 This callback reason indicates that a requested template has been
		   delivered in response to an request.  You must use to free the template when you have finished with it.

	 This callback reason indicates that a prior
		   call has completed, usually with a response from the daemon.

	 This callback reason indicates that event template information has
		   been delivered in response to an request.

		   The template is available in the structure.	You must use to free the template when you have finished with it.

FILES

       Header file that contains the event declaration, structures, and prototype
			   for the callback function

SEE ALSO

   Routines
       EvmConnCheck(3), EvmConnCreate(3), EvmConnSubscribe(3), EvmEventPost(3).

   Event Management
       EVM(5).

   Event Connection
       EvmConnection(5).

EVM Events
       EvmEvent(5).

																    EvmCallback(5)