Re: design problem, a general message passing class

On Jun 17, 10:36 pm, Ethan <ethan.li...@gmail.com> wrote:


You're a little vague as to exactly what you
are doing. Are you trying to create
a generic communications library? Or
are you implementing a specific protocol on
top of various transport protocols. Or
is there some specific data service,
available over networks, which you're trying
to make available via a client API that
will also handle the networking?

If you're creating a generic comms library,
you'll have the problem that different
transport protocols behave differently.
TCP and UDP, for instance, are very different,
and I don't see how these differences can
be made "transparent" to the application.

Even if you're just writing a client API
(analogous to, say, the Oracle client libraries),
"hiding" the data transport makes life a lot
harder for the application. In my work,
I've had to work with a number of such APIs,
and they were always unsatisfactory. Some
of the problems:

-- inadequate error reporting, or reporting
    in a way that was incompatible with our
    applications.

-- inadequate or non-existent monitoring
    capabilities.

-- assumptions about network set-up which demand
    special network configurations and extra code
    to get around.

-- requirements on system set-up that were
    incompatible with the rest of our applications.
    (For example, requiring a specific directory
    structure, specific files, etc.)

-- interface written assuming an application
    structure that was incompatible with our applications.

Not to mention the usual ones: can't compile on
our system, crashes or hangs, can't handle our networks, etc.

I've actually (re-)implemented a "generic" comms
API for our applications at work, but I had the advantage
that I already knew our applications' requirements, I
already knew how we set up networks, and, since I
wrote it, if any new requirements come along, I just
modify the code.

And the API doesn't really hide the transport layer,
it just tries to set up a suite of calls that can be
used either for UDP or for TCP, albeit not always with
the same meaning.

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