OSF DCE Application Development Guide--Core Components

Chapter 3. DCE Application Messaging
Message generation by distributed programs can be divided into two broad kinds:
• ‘‘Normal’’ (often user-prompted, client-generated) messages
• ‘‘Server event’’ messages, containing information about server activity, either
normal or extraordinary
Similarly, DCE makes available to applications two messaging APIs:
• The DCE messaging interface
• The DCE serviceability interface
The DCE serviceability interface is designed specifically to route messages of the second
type; it is described in Chapter 4. Messages in the first category are output using the
DCE general-purpose application messaging routines, which are the subjects of this
chapter.
Although the two interfaces, broadly speaking, do the same general thing (that is, write
messages), their functionality was designed to serve different needs, both of which occur
in most distributed applications. Nevertheless, either interface can be used more or less
exclusively of the other, if desired.
3.1 DCE and Messages
A message is a readable character string conveying information about some aspect of a
program’s state or activity to a human audience. Messages may be purely informational
or they may be intended to be responded to (that is, be ‘‘interactive’’). Prompts, error
displays, warnings, logs, announcements and program responses are all various kinds of
message.
DCE applications can simply use the standard output routines (such as printf(),
sprintf( ), and so on) for messaging. However, DCE provides two message interfaces
that automatically and transparently take care of many of the special problems that
distributed application messaging can give rise to. These interfaces are used by the DCE
components themselves to implement their messaging.
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