Windows Server Program
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4.3. Controlling the WEBMCA Server via DDE
The WEBMCA program can be a server for a DDE (Dynamic Data Exchange). Many Windows
software packages can use the DDE standard protocols to communicate with other Windows
programs, for example GRAMS, FAMOS or LabVIEW. In the following the DDE capabilities of the
server program are described together with a demo VI („Virtual Instrument“) for LabVIEW. It is not
recommended to use the DDE protocol for LabVIEW, as a DLL interface is (optionally) available
which works much faster. The following should be seen as a general description of the DDE
conversation capabilities of the server program.
4.3.1. Open Conversation
application: WEBMCA
topic: WEBMCA-
Any application that wants to be a client of a DDE server, must first open the conversation by
specifying an application and a topic name. The application name is WEBMCA and the topic is
WEBMCA-.
4.3.2. DDE Execute
The DDE Execute command can be used to perform any action of the WEBMCA program. Any of
the Control command lines described in chapter 4.2 can be used. For example a sequence of
control commands saved in a file TEST.CTL can be executed by specifying the command:
RUN TEST.CTL
The WEBMCA program then executes the command and, after finishing, it sends an
Acknowledge message to the DDE client. This can be used for synchronizing the actions in both
applications.
Figure 4.7: Opening the DDE conversation with the WEBMCA server in LabVIEW
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