DDE is an abbreviation for Dynamic Data Exchange. DDE is a communication protocol designed in Microsoft that enables to change data between the applications in Microsoft Windows operation system. The applications uses client-server interaction. Server is the application that represents a data source and is able to provides them on demand. Client is the application that requires this information.
For the purpose of data exchange, the client asks to connect to the server by specifying its name (server name) and description (or type) concerning the connection (topic). If server supports a required type of connection, it creates. The client can ask the information from server (it requires the logical name of information (item)).
For our purposes, the process DDE Server, source of data included in the information system, represents the server. From the view of DDE communication, the name of server is D_2000.
Supported type of connection (topic) could be for example VALUE (the complete list is stated in the particular chapter). is The names of objects in D2000 System are used for the logical name of required information (item).
When there are defined the conditions above mentioned, there can be possible to ask the real value of object in the system (e.g. Sec – current second) as follows:
D_2000|VALUE!Sec
DDE protocol is not case sensitive unlike the D2000 System.
Therefore, if there are the objects of name Sec and SEC in the
system, there is an ambiguity in DDE reference. This reference will acquire
the value "Ambiguous name”.
Note: D2000 DDE server supports only reading the values from D2000.
The writing values into the D2000 is not implemented.
Related pages:
Pridať komentár