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\title{{\bf DDE Client: }\\Dynamic Data Exchange for PLT Scheme}\index{DDEClient}\index{DDE Client}

\author{R. Matovinovic\\robert.matovinovic@web.de}
\date{October 31, 2006}
\maketitle

\begin{abstract}
This is the documentation for ddeclient a package providing DDE connectivity to PLT-Scheme. 
\end{abstract}

\tableofcontents

\vspace{2em}

{\small Copyright \copyright 2006 Robert Matovinovic 

Permission is granted to copy, distribute and/or modify this document and related files under the terms of the GNU Lesser General Public License, Version 2.1 published by the Free Software Foundation. A copy of the license is included in this document section ``License''.}
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\section{Introduction}

It enables DDE connectivity from within PLT-Scheme to other applications to control them and/or exchange data. Although DDE is a very old and not state of the art protocol there is still software around which can only communicate with other software via DDE. The use of such software was the reason for developing this package. 

This documentation does not introduce DDE but the use of the provided procedures. For using DDE with a certain program look at this program’s documentation. Because commands and examples how to communicate with it have to be provided there. The example program distributed with this package can be a good starting point to check out the commands and to see if you get what you want from the other application. There is a certain DDE terminology which might be unfamiliar to you. In that case have a look at the Glossary. For any questions, comments, suggestions and your user experience please contact me via email.

\section{Realization}

Ddeclient.ss relies on a C/C++ dynamic link library DDEClient.dll, which provides the DDE connectivity and exports the necessary C-functions and data. It's written for use with other programs as well, so if you are interested ask me for additional material like docs, header and examples. Ddeclient.ss imports the procedures of DDEClient.dll and provides easier to use procedures for scheme, that user's don't have to worry about freeing memory for example. A disadvantage over this approach is that data returned to the client is converted to scheme values by copying thus using additional memory.

\section{Features}

This package is beta release software.
\begin{itemize}
\item Enables DDE connections between one client up to 20 services/server applications. 
\item Request, execute and poke transactions can be performed synchronously and asynchronously.
Advise transactions are not implemented since I don't have any idea how they work and no examples to test.
\item Errors occurring during a conversation are reported and the the program is terminated. They are displayed in the interactions windows, if DrScheme is used.
\end{itemize}
\section{Requirements}
The package was developed and tested under Windows XP SP2 and PLT Scheme 350.4. Anything higher should work anything lower since the introduction of the Foreign Function Interface should also work, but as always there is no guarantee in both directions.

\section{Files and Directories}

This package contains the following main files and directories:

\begin{itemize}
\item {\bf /docs} Directory of documentation files
\item {\bf /compiled} Directory for compiled module files
\item {\bf /dll} Directory for source and additional files of DDEClient.dll
\item {\bf /dll/DDEClient.dll} C/C++ dynamic link library for DDE connectivity
\item {\bf ddeclient.ss} Interface module between DDEClient.dll and PLT-Scheme
\item {\bf ddeclientsample.ss} Sample program
\item {\bf info.ss} Package specific file for installation
\end{itemize}

\section{Getting Started}

The package contains a sample file \verb\ddeclientsample.ss\. It's a commented module file which shows examples of the DDE procedures provided by \verb\ddeclient.ss\. It uses Microsoft Word as service application, since most Windows users will have it on their machines. 

Load \verb\ddeclientsample.ss\ in DrScheme with, 

\scm{
(require (planet "ddeclientsample.ss" 
                 ("mato" "ddeclient.plt" 1 0)))}
                 
Open Microsoft Word, make sure you have write access to your \verb/C:\/ drive and there is no file named \verb\test.doc\. If you don't have write access to \verb/C:\/ search for the file name \verb/C:\test.doc/ in \verb\ddeclientsample.ss\ and replace it with what ever suits you. The easiest way to open \verb\ddeclientsample.ss\ is to run the require expression above without having opened Word. This causes an error in the interaction window and you can click on its page icon to open the file. Read through the file. It provides a procedure \scm{(run)}. Type \scm{(run)} in the interaction window and look at the output. After that experiment with it, copy blocks and change them in your own programs.

To load \verb\ddeclient.ss\ into your own programs require it as follows:

\scm{(require (planet "ddeclient.ss" ("mato" "ddeclient.plt" 1 0)))}


\section{Structure of a DDE process}
To implement a DDE conversation you need to set up a number of steps which are described below.
As structure of DDE process in this document is regarded the set of commands which is needed for a successful DDE conversation. The procedures provides by ddeclient.ss have to be used as follows.

\begin{itemize}
\renewcommand{\labelitemi}{}
\item \scm{dde-init}\\* Initializes DDEML.dll, which provides the DDE features of the operating system
\begin{itemize}
\renewcommand{\labelitemii}{}
\item \scm{dde-connect}\\* Establishes DDE connection to a service 
\begin{itemize}
\renewcommand{\labelitemiii}{}
\item One or more of the following procedures do the actual DDE transaction:
\item \scm{dde-cmd}\\* universal command for execute, poke and request transactions
\item \scm{dde-request}\\* request for data
\item \scm{dde-request-string}\\* request for data as string
\item \scm{dde-execute}\\* execute a command in the service application, i.e. menu command to open a certain file
\item \scm{dde-poke}\\* send data to the service application
\end{itemize}
\item \scm{dde-disconnect}\\* Closes down the DDE connection to a service of a server, frees memory
\end{itemize}
\item \scm{dde-uninit}\\* Uninitializes DDEML.dll
\end{itemize}

\section{Procedures}

\subsection{List of procedure arguments}\label{pargs}
Most of the procedure arguments are the same ones for different procedures. They are described here together.

\begin{itemize}
\setlength{\itemsep}{0pt}
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\item \scm{conv}\newline 
[number] conversation number, returned by dde-connect, index number to refer to a certain dde conversation.
\item \scm{type}\newline	
[string] type of DDE transaction can be "execute", "poke" or "request".
\item \scm{item}\newline	
[string] the command you want to send to the service. I.e. to see what topics are available you can set it to ``topics'' in a request transaction, after connecting the service with the topic ``system'', but not all programs support this topic. The available commands are dependent on the service and topic. Look up the documentation of the service for information about them. Note: A major drawback of using DDEML.dll is that \scm{item} must not exceed 255 characters. If it is longer there will be an error.
\item \scm{data}\newline
[string] data you send by a poke command to the service.
\item \scm{format}\newline	
[string] format of DDE data. It determines in which format the data between the applications is sent. See \ref{CBF} below.
\item \scm{timeout}\newline 
[number] indicates the waiting time in milliseconds until the transaction waits to be finished before returning to the program. If the number is greater 0 and the service doesn't return in time the transaction is terminated. 0 indicates an asynchronous transaction, which means the transaction is waiting for the service's answer as long as it takes.
\item \scm{access}\newline	
[string] flag in which format DDE data is copied to DDEClient.dll variables. It is meant for convenience since a lot of conversations only use ascii strings. It can be \verb\"byte"\ or \verb\"string"\. Has to be \verb\"byte"\ in case strings other than ascii format should be read. In that case the returned byte-string has to be converted accordingly, i.e. by \scm{bytes->string/utf-8}.
\end{itemize}

\subsection{List of procedures}
\begin{itemize}
\item \scm{(dde-init)}\index{dde-init} \\*
Initialize DDEML.dll the basic dll for DDE. DDEML.dll is installed with the operating system, so normally there is nothing to do to access it. To be called once in a program before any other DDE procedure.
\item \scm{(dde-uninit)}\index{dde-uninit} \\*
End usage of DDEML.dll. To be called after the last dde procedure of a program.
\item \scm{(dde-connect service topic) -> number}\index{dde-connect} \\*
Establish a connection to a service for a conversation. Returns a number which distinguishes the conversation from others. Service is a string containing the name of a DDE server application, i.e. ``winword'', usually the service name is the name of the programs exe-file. Topic is a string of the topic the service is connected for. There are different themes over which you can communicate with the service. Often a topic is a file name which is currently open in the service application. Most servers support also a topic ``system''.
\item \scm{(dde-disconnect conv)}\index{dde-disconnect} \\*
Cancel a conversation and stop the connection to a service; meaning of argument see \ref{pargs}.
\item \scm{(dde-cmd conv type item data format timeout access) -> multiple}\index{dde-cmd} \\*
General procedure for execute, poke and request transactions, the communication with the service; meaning of arguments see \ref{pargs}. The return value depends on \scm{type} and \scm{access}. Only \scm{type = "request"} will have a return value. \scm{access = "byte"} returns data as byte-string. \scm{access = "string"} returns data as string.
\item \scm{(dde-request conv item format timeout) -> byte-string}\index{dde-request} \\*
Abbreviation of a dde-cmd request transaction, which returns DDE data as byte-string; meaning of arguments see \ref{pargs}. The byte-string leave the flexibility how the data are further analyzed to the programmer.
\item \scm{(dde-request-string conv item timeout) -> string}\index{dde-request-string} \\*
Abbreviation of a \scm{dde-cmd} request transaction, which returns DDE data as string; meaning of arguments see \ref{pargs}.
\item \scm{(dde-execute conv item timeout)}\index{dde-execute} \\*
Abbreviation of a \scm{dde-cmd} execute transaction, format is \verb/CF_TEXT/; meaning of arguments see \ref{pargs}.
\item \scm{(dde-poke conv item data timeout)}\index{dde-poke} \\*
Abbreviation of a \scm{dde-cmd} poke transaction, format is \verb/CF_TEXT/; meaning of arguments see \ref{pargs}.
\item \scm{(dc-dde-version) -> string}\index{dc-dde-version} \\*
returns a string with information about the version of DDEClient.dll.
\end{itemize}

\section{Supported Clipboard Formats}\label{CBF}
The following formats can be used to determine how the DDE data will be formatted between service and client. Microsoft uses clipboard formats to format data which is exchanged via DDE. Such it is possible not only to transfer text but also other data, for example pictures. If you use anything else than the \verb\CF_TEXT\ format your \scm{access} argument must be set to \verb\"byte"\ and you have to handle the resulting byte string on your own to get the desired data, which may be a lot of work. The formats themselves are described in the Windows SDK. There are a lot more formats but only the following are available through the DLL. Write the format strings in capitals exactly as they are given here.

\begin{itemize}
\item \verb\CF_TEXT\ \\	Null-terminated, plain ANSI text in a global memory block.
\item \verb\CF_BITMAP\ \\	A bitmap compatible with Windows 2.x.
\item \verb\CF_METAFILEPICT\ \\	A Windows metafile with some additional information about how the metafile should be displayed.
\item \verb\CF_SYLK\ \\	An ASCII text format used by some older Microsoft products.
\item \verb\CF_DIF\ \\ Software Art's data interchange format (DIF). Also an ASCII text format.
\item \verb\CF_TIFF\ \\	Tag image file format (TIFF) data in a global memory block.
\item \verb\CF_OEMTEXT\ \\	Similar to \verb\CF_TEXT\ but using the OEM character set.
\item \verb/CF_DIB/ \\	A global memory block containing a Windows device-independent bitmap (DIB) as a BITMAPINFO structure followed by the bitmap bits.
\item \verb\CF_PALETTE\ \\	A color-palette handle. (Used in conjunction with \verb/CF_DIB/.)
\item \verb/CF_PENDATA/ \\	Data is for the pen extensions to Windows.
\item \verb\CF_RIFF\ \\	Resource interchange file format (RIFF) data as a global memory block.
\item \verb\CF_WAVE\ \\	A specific case of RIFF in which the contained data is a waveform (sampled sound).
\end{itemize}

\section{Thanks}
Eli Barzilay and collegues thanks for the foreign function interface. Without it the project wouldn't be possible.

I owe a lot concerning the C/C++, DDE part of this project to the following people, companies  through their books or presence of their work on the internet:
\begin{description}
\item[www.angelfire.com/biz/rhaminisys/ddeinfo.html] for their info on DDE and their example archive xlddec.zip
\item[J\"urgen Wolf] and Galileo Computing for his very instructive book on C programming ``C von A bis Z'', at www.galileo-press.de/openbook/c\_von\_a\_bis\_z/
\item[Steven Randy Davis] for his book ``C++ for Dummies''
\item[www.functionx.com] who ever are behind it, for their perfect tutorial on creating dlls at www.functionx.com/visualc/libraries/win32dll.htm, I wouldn't have started without it.
\item[Faweb, Takebishi] for their DDE example at\\ http://www.faweb.net/us/ioserver/sample\_vc.html
\item[Graeme S. Roy] for his library mpatrol to check this dll for memory leaks at www.cbmamiga.demon.co.uk/mpatrol/
\item[Robert Schmitt] for his article and binaries to get mpatrol started so quickly at www.codeguru.com/cpp/w-p/win32/tutorials/article.php/c12231/.
\item[Microsoft Knowledgebase] for some articles like KB279721, but the DDE documentation is mostly quiet unreadable in my opinion.
\end{description}

\section{Glossary}
\begin{description}
\item[Client]\index{client} Application that asks for the conversation, here the scheme program.

\item[Service]\index{service} In earlier times called server, the application which is to be controlled or serves the client with data. It is normally the name of the application's exe-file, example: \verb/"winword"/.

\item[Transaction]\index{transaction} The interaction between client and server, which is of a certain type like \verb/"request"/, \verb/"execute"/, \verb/"poke"/.

\item[Conversation]\index{conversation} The connection and what happens between client and service. Since a client can have more than one conversation at the same time with different services each conversation is indexed by a distinct number.

\item[Synchronous transaction]\index{synchronous} In a synchronous transaction the client sends a transaction to the service and waits a certain time for the service to finish. It returns the control to program only if the service finishes the transaction or if the timeout reached.

\item[Asynchronous transaction]\index{asynchronous} In an asynchronous transaction the client does not wait for the service to answer, but returns the control to the program after sending the transaction. To get the data the program has explicitly to ask if the service has returned data. This kind of transaction is preferable if the duration of a transaction is not known. The dde-... commands handle asynchronous transactions in a way that they seem to be synchronous transactions without a timeout. This is very convenient for a lot of applications. 
\end{description}

\pagebreak
\section{License}

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\begin{center}
NO WARRANTY
\end{center}

  15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
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\begin{center}
END OF TERMS AND CONDITIONS\\
\vspace{2ex}
How to Apply These Terms to Your New Libraries
\end{center}

  If you develop a new library, and you want it to be of the greatest
possible use to the public, we recommend making it free software that
everyone can redistribute and change.  You can do so by permitting
redistribution under these terms (or, alternatively, under the terms of the
ordinary General Public License).

  To apply these terms, attach the following notices to the library.  It is
safest to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least the
``copyright'' line and a pointer to where the full notice is found.

\begin{quote}
    \verb/</one line to give the library's name and a brief idea of what it does.\verb/>/\\
    Copyright (C) \verb/</year\verb/>/  \verb/</name of author\verb/>/

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
\end{quote}

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your
school, if any, to sign a ``copyright disclaimer'' for the library, if
necessary.  Here is a sample; alter the names:

\begin{quote}
  Yoyodyne, Inc., hereby disclaims all copyright interest in the
  library `Frob' (a library for tweaking knobs) written by James Random Hacker.

  \verb/</signature of Ty Coon\verb/>/, 1 April 1990\\
  Ty Coon, President of Vice
\end{quote}
That's all there is to it!


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\end{document}
