Browse Prior Art Database

Dynamic Data Exchange Flash Link

IP.com Disclosure Number: IPCOM000106024D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Roberson, KW: AUTHOR

Abstract

Dynamic Data Exchange (DDE) is a protocol that can be used for communications between a client and a server application. To start the connection the client issues a DDE_INITIATE message that is broadcast to every registered application in the system. Each application in an asynchronous fashion receives the messages and tests it to see if it is the requested server. If it is not, then the message is passed on to the next application. If it is the needed server, an acknowledgement is sent back to the client. At this point the connect is complete and data/commands can be sent/posted between the two.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Dynamic Data Exchange Flash Link

      Dynamic Data Exchange (DDE) is a protocol that can be used for
communications between a client and a server application.  To start
the connection the client issues a DDE_INITIATE message that is
broadcast to every registered application in the system.  Each
application in an asynchronous fashion receives the messages and
tests it to see if it is the requested server.  If it is not, then
the message is passed on to the next application.  If it is the
needed server, an acknowledgement is sent back to the client.  At
this point the connect is complete and data/commands can be
sent/posted between the two.

      When it comes time to disconnect the communications link, the
client posts a DDE_TERMINATE message to the server.  The server in
turn posts an acknowledgement back to the client.  The connection is
now terminated and the server is free to connect to other client
applications.

             Current DDE Connect/Disconnect Diagram

            +--------------+            +-----------+
            | Client App.  |            |Server App.|
            |--------------|            |-----------|
            |*DDE_INITIATE |----------->|           |
            |      .       |<-----------| DDE_ACK   |
            |      .       |            |     .     |
            |      .       |            |     .     |
            | DDE_TERMINATE|----------->|     .     |
            |              |<-----------| DDE_ACK   |
            +--------------+            +-----------+

*Note:    The DDE_INITIATE message is sent to all application
          asynchronously.  In other words, the message is passed from
          one application to the next until one application responds
          or all applications have seen it.

      If the client application needed to reconnect with the same
server the original connection steps would be executed and the
DDE_INITIATE message would be sent to every application again.  The
repeated connection and disconnection from the server waists an
enormous amount of CPU cycles and system resources.  In the DDE Flash
Link, two new messages, DDE_SUSPEND and DDE_RESUME, are added to the
predefined list of DDE messages.

      The DDE_SUPEND message is used in place of the DDE_TERMINATE
message when trying to close down a communications session.  The
client posts the DDE_SUSPEND message to the server and remembers the
servers handle.  The server treats the DDE_SUSPEND as a normal
DDE_TERMINATE message except that the server remains active in the
system.  Other client application may connect with the server at this
time.

      The DDE_RESUME message is used by the cli...