EvmConnection man page on HP-UX

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EvmConnection(5)					      EvmConnection(5)

       EvmConnection - connection to the EVM (Event Management) daemon

       An  EVM	connection  is the context through which data is passed to and
       from the EVM daemon.  A connection has the following attributes:

       ·  Connection Type

       ·  Response Mode

       ·  Transport Type

       ·  Callback, and associated Callback Argument

       ·  Connection Context

       These attributes are described in the following sections.

       An EVM client is any program that processes events through the EVM dae‐
       mon.   EVM  supports  three  distinct types of client: posting clients,
       subscribing (listening) clients, and service  clients.	Regardless  of
       type, all clients connect to the EVM daemon in the same way.

   Connection Type
       The  type  of connection established determines the client type.	 There
       are associated constants to be used when the connection is created.

       The client uses this connection to post events to the daemon  for  dis‐

       The client uses this connection to listen for events distributed by the

       The client uses this connection to request that the daemon provide a
		 service, such as retrieve events from a log.

		 A client may use all three  types  of	connection,  but  must
		 establish each connection separately.

   Response Mode
       The response mode associated with a connection determines the manner in
       which certain API functions will deal with the  daemon's	 responses  to
       request	messages.   See	 the  EvmConnCreate(3) reference page for full
       details of each mode.  The modes are:

       The API functions will return as soon as the request has been sent to
		 the daemon, and the caller  will  not	receive	 the  daemon's

       The API functions will send the request to the daemon, and wait until a
		 response  has	been  received before returning to the caller.
		 The returned status code will reflect the response.

       The API functions will return as soon as the request has been sent to
		 the daemon, and the caller must monitor the connection for  a
		 response.   When  the	response is received, the connection's
		 callback function will be invoked to handle it.

   Transport Type
       The transport type specifies the type of connection to be made  to  the
       daemon.	The only valid connection that can be made is:

       Connection  is through a domain socket to a daemon running on the local

       This attribute specifies the function you want to handle	 any  incoming
       responses resulting from activity on the connection. Callbacks are dis‐
       cussed in more detail  in  the  EvmCallback(5)  reference  page.	  This
       attribute is valid only when the Response Mode is

   Connection Context
       This  attribute	is a handle to a connection returned when a connection
       is created. You must pass this handle to all other functions  you  call
       which need to access the connection.

   Connection Monitoring
       Once  you  have	established  a connection, the API functions will take
       care of all communication activity with the daemon. However,  you  must
       make sure that these functions get an opportunity to do their work when
       activity occurs. EVM provides several ways for  you  to	do  this.  The
       method you choose depends on the model of your program.

       ·  If  your  program  is I/O driven, waiting for I/O to occur on one or
	  more file descriptors, handling  activity  as	 it  occurs  and  then
	  returning  to wait for more I/O, it probably spends most of its time
	  in a call.  In this case, you should use  to	establish  which  file
	  descriptor  the  EVM connection is using, and then include that file
	  descriptor in your read mask.	 When you detect activity on the  con‐
	  nection, invoke to handle the activity.

       ·  If your program is driven purely by activity on a single EVM connec‐
	  tion, you can let the API handle the I/O entirely by using  to  wait
	  for activity to occur on the connection.  When the function returns,
	  dispatch the I/O using and then return to

       ·  If your program is driven in some other way, and there  are  certain
	  points  (for	example, at the end of some control loop) at which you
	  want to handle EVM activity, you can call to check for any outstand‐
	  ing activity.	 If this function indicates that there is something to
	  do, you can call otherwise you can continue immediately with	normal

   Destroying a Connection
       When  you  are finished with the connection, use to disconnect from the
       daemon.	It is important to check the return  status  for  any  failure
       each  time you call a connection function and destroy the connection if
       a failure occurred.  The file descriptor associated with the connection
       remains	open  until you destroy the connection even if I/O errors have
       been detected on the connection.


       EvmConnControl(3), EvmConnCreate(3), EvmConnFdGet(3),  EvmConnCheck(3),
       EvmConnWait(3), EvmConnDispatch(3), EvmConnDestroy(3).

   Event Management

   Event Callback

   EVM Events


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