8.2. DDE

Cascade DataHub™ : Version 5.4
	Chapter 8. Properties Window

This option in the Properties Window sets up the Cascade DataHub to act as a DDE client and/or DDE Server for DDEAdvise messages. For more information on DDE, please refer to Section 2.3.1, “DDE Protocol” and Appendix F, DDE Overview.

DDE Client

To act as a DDE client, check the Act as a DDE client box. To add a new service or topic, press the Add button. To edit a service/topic, double-click it or select it and press the Edit. To remove a service/topic, select it and press the Remove button.

Double-click a selection, or pressing the Add or Edit button opens the DDE Item Definition Window:

Here is what must be entered:

Connection Name: A name used by the Cascade DataHub to identify the connection. There should be no spaces in the name. It doesn't matter what name is chosen, but it should be unique to other connection names. Each connection can have only one Service and one Topic, but it can have multiple Items.
Service: The service name of the DDE server to this client.
Topic: The DDE topic under which the data will be sent.
Item Names: The DDE item name, which corresponds to a point name in the Cascade DataHub. If that point doesn't exist in the DataHub, it will be created. Enter a name for each item and press the Add button to add items. To remove an item, highlight it and press the Remove button. Once all the information is entered correctly, press the OK button to enter the definition.

DDE Server

To have the Cascade DataHub act as a DDE server, check the Act as a DDE server box. The default service name is datahub.

To add a DDE service name to the list, click the Add button and enter the name in the DDE Service Window:

To edit a DDE service name, double-click it or select it and press the Edit. To remove a DDE service name, select it and press the Remove button.

It is currently possible to have more than one instance of the Cascade DataHub, with one or more DDE service names in common, running on a single machine. If you plan to configure a system like this, you should ensure that each instance of the DataHub has unique domain names. Otherwise, when any two of those DataHubs are acting as servers, it is not possible to predict which one of them a given client will send data to.