Closing DDE conversations

You can close a DDE conversation in one of three ways:

Invoke the DDE TERMINATE statement for the conversation

Leave the scope of the DDE frame that owns the conversation

Terminate or remove the DDE server or server topic associated with the conversation

Regardless of how you close a DDE conversation, once closed, the channel number for that conversation is no longer available for further exchanges. Terminating the conversation with the DDE TERMINATE statement has no effect on other conversations open for the same DDE server or frame. They continue without interruption.

In general, if your OpenEdge client creates and manages a server environment for the conversation, it should also clean up that environment when closing the conversation. For example, the following code fragment cleans up a Microsoft Excel server environment when the user presses a QUIT button. The client removes an advise link to the worksheet and closes the conversation for that worksheet topic (sheet). Then using the System conversation (sys), it executes server commands that close the documents opened for the conversation, clear Excel error checking, and instruct the server to shut itself down. For example:

DEFINE VARIABLE sys AS INTEGER NO-UNDO.
DEFINE VARIABLE sheet AS INTEGER NO-UNDO.

DEFINE BUTTON bq LABEL "Quit".
...

ON CHOOSE OF bq IN FRAME MainFrame DO:
...
DDE ADVISE sheet STOP ITEM "r4c2".
DDE TERMINATE sheet.
DDE EXECUTE sys COMMAND "[activate(~"sheet1~")]".
DDE EXECUTE sys COMMAND "[close(0)]" 0).
DDE EXECUTE sys COMMAND "[activate(~"chart1~")]".
DDE EXECUTE sys COMMAND "[close(0)]".
DDE EXECUTE sys COMMAND "[error(0)]".
DDE EXECUTE sys COMMAND "[quit()]".
END.
...

Note: The tilde (~) is used to escape embedded quotes in strings, for example, ~"sheet1~".