Technical Reference Manual - InduSoft

Communication with Other Devices
Configuring a DDE Client connection to a DDE Server
The DDE Client task/worksheet is used to configure a DDE Client connection to a DDE Server application
such as Microsoft Excel (or any other Windows program supporting this interface).
Dynamic Data Exchange (DDE) is a protocol for dynamic data exchange between Windows applications, such
as Excel. A DDE conversation is an interaction between server and client programs. IWS provides interfaces
that run as clients or as servers. See DDE Client Runtime and DDE Server in the Runtime Tasks (Tasks on the
Home tab of the ribbon).
• To run as a server, start the DDE or NetDDE server task as described in Runtime Tasks.
• To run as a client, configure the DDE interface worksheet on the Comm tab.
Network Dynamic Data Exchange (NetDDE) is an extension of DDE that works across computers on a
network.
• To run IWS as a server to a NetDDE connection, you must start the DDE Server application.
• To run IWS as a client to a NetDDE connection, use the same DDE interface worksheets with the proper
configuration to address a IWS project.
Note: When running NetDDE, IWS accepts the WRITE triggers only. To read data, you must
configure a write command on the server computer.
To open a new DDE worksheet, right-click on the DDE folder and click the prompt screen.
A new DDE worksheet displays, as in the following figure.
The DDE worksheet dialog is divided into two areas:
DDE Worksheet
• Header area (top section), contains information for the whole group and defines the tags to start the
reading and writing and to receive connection status
• Body area (bottom section), where you define tags in the project and items related to the DDE server
application
Every DDE interface is based on addressing an application using the following three structures:
• Application Name
• Topic
• Item
The first task is to find these identifiers in the DDE Server application.
Use the parameters in the DDE client worksheet Header area as follows:
• Description field: Type a description of the DDE worksheet for documentation purposes.
• Application Name field: Type the DDE server application name.
• Topic field: Specify a topic in the server application.
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