Using CitectSCADA > Exchanging Data with Other Applications > Using DDE Trusted Shares > Using network DDE

Using network DDE

Microsoft Network DDE Service needs to be running on both computers to communicate using Network DDE. For startup details, see Starting network DDE services.

Before a Network DDE Client can establish a DDE conversation with a Network DDE server application, the Network DDE server application computer needs to already have setup a Network DDE Share. For details, see Setting up network DDE shares.

Note: You cannot connect using Network DDE to a shared application on the same machine. You can only connect using Network DDE to a shared application on another machine (which needs to also be on the same network).

To connect to a Network DDE shared application, you use an altered version of the DDE syntax, which replaces the "<ApplicationName>" with "<ComputerName>\NDDE$" and replaces the "<TopicName>" with the Network DDE server Share "<ShareName>", and continues to use the "<DataItemName>" as normal.

At first glance, there appears to be no way to specify the DDE Application or Topic names in the Network DDE syntax call, and indeed, that is the case. However, the DDE Application and Topic names are defined in the DDE server Share settings. So, when the Network DDE server machine receives the call (from the Network DDE Client) containing the Share name, it knows which application and topic to connect with. See Connecting to a network DDE shared application.