The (autoload) library dde.pl defines primitives to realise simple DDE server applications in SWI-Prolog. These features are provided as of version 2.0.6 and should be regarded prototypes. The C-part of the DDE server can handle some more primitives, so if you need features not provided by this interface, please study the library dde.pl.
+Service(+Topic, +Item, +Value)Service is the name of the DDE service provided (like progman in the client example above). Topic is either an atom, indicating Goal only handles requests on this topic or a variable that also appears in Goal. Item and Value are variables that also appear in Goal.
The example below registers the Prolog feature/2 predicate to be accessible from other applications. The request may be given from the same Prolog as well as from another application.
?- dde_register_service(prolog(feature, F, V), feature(F, V)). ?- open_dde_conversation(prolog, feature, Handle), dde_request(Handle, home, Home), close_dde_conversation(Handle). Home = '/usr/local/lib/pl-2.0.6/'
Handling DDE execute requests is very similar. In this case the template is of the form:
+Service(+Topic, +Item)
Passing a Value argument is not needed as execute requests either succeed or fail. If Goal fails, a `not processed' is passed back to the caller of the DDE request.