If your program is a posting client, you must
choose a policy for connecting to the EVM daemon. You can choose one
of the following options:
Create a connection when the program starts, and maintain
it until the program terminates (permanent connection).
Create a connection each time that you need to post
an event, and destroy it immediately afterwards (transient connection).
The cost in processing time of creating an EVM
connection is significant, because the setup and authentication protocol
require several message transactions as well as some file I/O. As
a general rule, you must maintain a permanent connection if you want
to post events frequently during normal program operation. If you
choose this option, your code must handle unexpected disconnection
if the EVM daemon is terminated. For information about handling disconnection,
see “Handling Disconnections”.
If you expect to post events infrequently —
for example, only if unexpected errors occur — consider using
a transient connection. Although a transient connection is more expensive
in set-up time if multiple events are posted, it eliminates both the
system resource cost of a permanent connection and the need for your
code to deal with an unexpected disconnection. The simplest way to
post events to the local daemon with a transient connection is to
pass NULL as the connection argument to EvmEventPost or EvmEventPostVa.
If you do not require a permanent connection,
but you expect to post several events over a short period under some
circumstances; consider creating a temporary connection that you will
destroy when the activity is completed, rather than posting successive
events using a separate connection for each.
Subscribing clients must maintain permanent connections
to be assured of receiving events.
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