Q92829: DDEML Samples Using Microsoft Foundation Classes

Article: Q92829
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0,3.1
Operating System(s): 
Keyword(s): kbfile kbprogramming kbsample kbDDE
Last Modified: 09-FEB-2000

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

CDDEML is a set of two sample applications that demonstrate a DDEML client and a
DDEML server. They are written using the Microsoft Foundation Class Libraries
(MFC) and define new classes for handling DDEML.

The following files are available for download from the Microsoft Download
Center:

Cddeml.exe

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.


MORE INFORMATION
================

This sample contains two applications that demonstrate a DDEML server and DDEML
client in MFC applications. This sample defines four new classes to help
implement the DDEML support. These classes are:

  CDDEClient
  CDDEClientConv
  CDDEServer
  CDDEServerConv

The CDDEClient and CDDEServer classes encapsulate the functionality of a DDEML
client or server. CDDEClientConv and CDDEServerConv encapsulate individual
conversations that are managed by the CDDEClient or CDDEServer class. The
CDDEClient and CDDEServer classes maintain a map of the current conversations
according to the conversations handle. Using this map, the server or client can
look up any ongoing conversation based on its handle.

These classes were designed to implement DDEML in a very general way. As a
result, these classes don't do much by themselves; they are designed to be
reused in an application by deriving from each of these classes. Typically, an
application derives one class from CDDEClient or CDDEServer. This derived class
contains details such as what conversations are supported and how to handle
callbacks that do not relate to a specific conversation. Usually there is only
one instance of this class in an application. An application may derive many
classes from CDDEClientConv or the application supports. These derived classes
implement how each conversion handles callbacks. They also may contain buffers
to store data from the conversation, or pointers to other objects that they need
to communicate with. This sample contains a client and server application built
using the classes mentioned above.

One difficulty in writing DDEML classes is how to handle the DDEML callback
function. In this sample, the DDEML callback function is contained in the
CDDEClient or CDDEServer class. The callback function first checks to see
whether the transaction is for the client or server, or for one of the
conversations. If it is for the client or server, then the callback function
calls the member function that handles that transaction. If the transaction is
for a conversation, then the callback function looks up the pointer to the
conversation object using the handle of the conversation in the conversation
map. Then it calls the member function of the conversation that handles that
transaction. Therefore, by using these classes, an application developer does
not need to write a DDEML callback function.

Additional query words: 3.00 3.10 softlib CDDEML.EXE

======================================================================
Keywords          : kbfile kbprogramming kbsample kbDDE 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.