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Q152087: Connpts.exe Implements Connection Points in MFC Apps

Article: Q152087
Product(s): Microsoft C Compiler
Version(s): 4.0,4.1,5.0,6.0
Operating System(s): 
Keyword(s): kbfile kbSample kbConnPts kbMFC kbVC400 kbVC410 kbVC500 kbVC600 kbGrpDSMFCATL
Last Modified: 26-JUN-2002

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
   - Microsoft Visual C++.NET (2002) 
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SUMMARY
=======

This sample demonstrates implementing connection points and connection point
sinks in MFC applications. The two applications that make up this sample are the
"source" application that implements a connection point, and the "sink"
application that implements an interface that will be hooked up to the
connection point.

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

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

Visual C++ 6.0:

The following file is available for download from the Microsoft Download Center:

  DownloadDownload Connpts.exe now
  (http://download.microsoft.com/download/vc40std/sample/5/WIN98/EN-US/Connpts.exe)

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

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.

Visual C++ .NET:

The following file is available for download from the Microsoft Download Center:

  DownloadDownload Connptsvcnet.exe now
  (http://download.microsoft.com/download/visualstudionet/sample/1.8/win98mexp/en-us/Connptsvcnet.exe)

Release Date: June 25, 2002

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

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.


NOTE: Use the -d option when running CONNPTS.EXE to decompress the file and
re-create the proper directory structure.

Registration of the Connection Point Interfaces
-----------------------------------------------

To run the sample, the connection point interfaces must be registered because
this sample demonstrates using the connection point interfaces across process
boundaries and, in this case, the interfaces must be marshaled. You may or may
not need to install marshaling DLLs on your system. For more information on
resolving this issue, please see the following article in the Microsoft
Knowledge Base:

  Q149231 CXPRX: Marshaling Code for Connection Point Interfaces

Connection Points and Sinks
---------------------------

For a more detailed understanding of connection points, consult the documentation
in the References section below.

A COM object has interfaces that can be called by clients of the object. These
are called incoming interfaces. The connection point interfaces are a means for
this object to call back into the clients via outgoing interfaces. Typically,
the object will want to notify any of its clients of some event or change in the
object's state. The object in this case is known as the source, and the client
is known as the sink.

To enable communication using the connection point mechanisms, the source object
will implement one or more connection points, such as an object that supports
IConnectionPoint, and the sink object will implement an interface that the
source object knows how to call. It is the job of the connection point to hold
on to the address of the interface in the sink object so that the source can
call it. The connection point may actually hold on to more than one address if
multiple sinks are clients of the object. This is called multicasting. There
will be one connection point in an object for each sink interface the object
knows how to call.

The remaining interface is IConnectionPointContainer. IConnectionPointContainer
is implemented in the source object and serves to contain and manipulate the
object's connection points.

This sample closely models the functionality of event notifications in OLE
Controls. The sink in this sample implements an IDispatch interface, as would a
control container, that the source knows how to use. You will need to identify
this interface with a unique IID so a connection point for the interface can be
uniquely identified. You will be able to take advantage of the IDispatch
marshaling code to marshal the dispatch interface across process boundaries.

Note that the sink does not have to implement a dispatch interface. If you choose
to implement your own interface, however, and you are going to cross process
boundaries, you will be responsible for marshaling the interface.

Running the Sample
------------------

Once the connection point interfaces are registered, the sample can be run. Run
the "source" application first. Each of source's open documents is an event
source. Run the "sink" application next. In sink, select Sink / Attach Source
from the document menu. Note that each open document in sink is an event sink.
You should see a list of available sources. If you do not, the connection point
interfaces are not correctly registered. Select any sources that you would like
to connect to. A sink may attach itself to any number of sources and a source
may have any number of sinks attached. From the source document menu, select
Events / Fire Event *. Any sinks that are hooked up to the source should display
a message indicating that the event was received.

Miscellaneous Notes
-------------------

This sample implements connection points across process boundaries. Implementing
this functionality in in-process objects is done in the same manner. In-process
implementation will not require that you register the connection point
interfaces or the interface that is implemented by the sink.

In this sample, the sink interface and the connection point interfaces need to be
registered. This registration is taken care of in the InitInstance function of
the sink application.

An IID for the sink interface is made available to both the sink and source
applications. Please note that the .cpp file in which this interface is defined
does not use pre-compiled headers.

All code in this sample relevant to the connection point implementation is
blocked by "//SAMPLECP" and "//END SAMPLECP" blocks. This coding convention
should make it easy to identify what you will need to implement in your code.

REFERENCES
==========

"Inside OLE" by Kraig Brockschmidt, Second Edition, Chapter Four - Connectable
Objects, published by Microsoft Press.

Programming with MFC: Encyclopedia - Connectable Objects

Additional query words: Connection Point kbole kbMfc kbVC400 kbVC410 kbVC500 kbDSupport kbdsi connpts connptsvcnet

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Keywords          : kbfile kbSample kbConnPts kbMFC kbVC400 kbVC410 kbVC500 kbVC600 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : :4.0,4.1,5.0,6.0
Issue type        : kbhowto

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