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About DDE
About NetDDE
2 • • • • Chapter One - Introduction
DDE is the acronym for Dynamic Data Exchange, a communications protocol that
allows independently developed Microsoft Windows 2000 SP2 programs to share
data and instructions with each other.
DDE implements a client-server relationship between two concurrently running
programs. The server application provides data and accepts requests from any other
applications interested in its data. The applications requesting the data are called
clients.
Requests for data can be of two types: one-time requests or permanent data links.
With one-time requests, the client program requests a "snapshot" of the desired data
from the server application. An example of a one-time request is a program such as
Excel running a report-generating macro. The macro opens a temporary link to
another application, requests specific data, closes the link, and uses the data to
generate the report.
Permanent data links are called hot links. When a client application sets up a hot link
to another application, it requests the server application to advise the client whenever
a specific item's data value changes. Hot links remain active until either the client or
server program terminates the link. Hot links are an efficient means of exchanging
data because, once the link has been established, no communication occurs until the
specified data value changes.
The DDE protocol specification includes standardized formats for messages to be
exchanged between DDE-compliant applications (such as Microsoft Excel).
NetDDE for Windows 2000 SP2 is an extension to DDE. With NetDDE, client
applications do not have to be running on the same PC as the DDE Server; a client
application on one PC may request data from a DDE Server operating on another PC.
Its capabilities include communication over local-area networks and through serial
ports.
Two or more networked IBM-compatible PCs running Windows 2000 SP2 are
required to run NetDDE. The version of NetDDE which is supplied with Windows
2000 SP2 is the recommended version; other versions of NetDDE are not
recommended for use with PMCS.
DDE Server User's Guide
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