Black Box GEH-6510 manual About DDE, About NetDDE

About DDE

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-serverrelationship 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).

About NetDDE

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.

2 • Chapter One - Introduction DDE Server User’s Guide