capi20proxy: capi forwarding over tcp/ip networks
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1.0: Intro

Welcome to the homepage of the CAPI 2.0 Proxy project. This project, founded in early 2002 by Adam Szalkowski aims towards creating a network forwarding software CAPI 2.0 (ISDN) messages over a TCP/IP-based net- work.
Such software can be very useful in local area network environments, e.g. in a company intranet, where CAPI services such as Fax, Telephone and Data Transmissions are to be made available to a number of clients using only one ISDN Adaptor.
The CAPI2.0Proxy Team is right now creating several client and server implementations for both Microsoft Windows 9x/ME/NT/2k/XP and GNU/Linux. Ports to *your-choice-here*BSD and MacOS (X) have not yet been started but could theoretically be derived from the Linux code.
Enjoy our software and tell us if you have any problems or need other help.

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2.0: Technical Description

Applications running on the client computer send requests to the capi2032.dll (Windows) or kernelcapi (Linux). This message might for example be a command to send of a Fax or to create an Internet Connection. But the CAPI20Proxy has replaced capi2023.dll by a new library which redirects the Application's request over a network to another computer running the server software. The server receives the request, parses it and calls his capi2023.dll (a "real" one) or his linux-kernelcapi with the parameters he got from the client. The reply form the CAPI software (maybe an error code or an incoming Fax) is sent back to the client, whose user-land application should be able to "understand" the incoming data.

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3.0: Windows Implementation Specific Notes

The Windows implementation of CAPI20Proxy is pretty functional both on the client and on the server side. It should be possible to use almost every normal CAPI application using it. There are some issues related to network speed which make Telephony quite a horrible thing but we hope to be able to improve our program performance so this will be possible one day.

3.1: Installing The Windows Client Software

  • Download the latest binary release of this CAPI 2.0 Proxy Client from Sourceforge. Unzip the capi20proxy-win32-client-*.zip to some location. Eventually make a backup of your existing c:\windows\system\capi2032.dll or c:\winnt\system32\capi2032.dll.
  • Close all applications using the CAPI interface
  • Copy the capi2032.dll from the .zip file into your c:\windows\system or c:\winnt\system32 directory.
  • Execute the capi20proxy.reg
  • Adjust the settings in HKEY_LOCAL_MACHINE/Software/The Red Guy/capi20proxy/
  • Start some CAPI application to test
  • 3.2: Installing The Windows Server Software

  • Download the latest binary release of this CAPI 2.0 Proxy Server from Sourceforge. Unzip the capi20proxy-win32-server-*.zip to some location.
  • Copy the capi20server.exe from the .zip file into your c:\windows\system or c:\winnt\system32 directory.
  • On NT execute "capi20server -i" to install it as a service (you must be admin) and start the service or reboot your system.
  • On 9x execute "capi20server" to run the server

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    4.0: Notes For Penguin People

    The Linux implementation is splitted up a bit: Linux Server and Linux Client are completely seperated programs. And while Linux Server somehow works (a bit), Linux Client still needs some major coding.

    4.1: The Linux Client Software

    The client module seems to be devolped quite far. I was able to load it into my kernel without crashing it.
    This module offers a quite generic interface for user mode daemons to supply virtal CAPI controllers. This could be eventually used by other LAN CAPI implementations.
    As the client daemon has not been started yet, the module cannot be debugged very well.
    We're searching people who would test the module.

    4.2: The Linux Server Software

    The Linux Server is currently not maintained in SourceForge CVS but on my private server at You can get my latest development versions which have been heavily improved there. They're smaller, faster and include tons of new stuff..

    Linux Server has been working pretty fine for some time now, so I am tried to say that it's BETA software, altough any serious Linux guru would probably break out into laughter and rate the code as PRE-ALPHA.
    As I am in serious warfare with CVS, I do not maintain the source there but rather keep it on my Harddisk, so you'll be forced to use the released files from the SFdownload site.

    Here's some brief install info, please read the manual (README):
  • Get the latest release from
  • Open a cosole window and untar the archive: tar xvfz >filename<.tar.gz.
  • Change to the newly created directory. Open README in your favourite text editor (VIM, of course) and read it.
  • Change to src/ and type make all install .
  • You might need to change the init script /etc/init.d/capifwd to fit your disribution (it's been tested in Debian).
  • Now add the script to your rc*.d or start the server manually by executing /usr/sbin/capifwd.

  • Need help installing the CAPI driver for your Fritz!Card?

    If this link should not work try to search in Google for: "fcpci linux capi alias howto"

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    5.0: Getting Help and Helping

    5.1: Questions, bug reports and love letters.

    Well, uhmm... We're not a support club but we try to quickly answer any questions asked. Send email to This is our 24/7 support hotline. Describe your problem verbosely and give us any output and system information you have.

    Or try this:
    Yur fucking bullshit fucktup my hole server!  assholes!
    why do you produce such crap? cant ya code proper stuff?>????!
    how do i repair this my system is completly wrcked!

    5.2: Join

    Do you code C/C++ and do you use CAPI? Are you simply unemployed or have a load of free time? Welcome! We need people to improve the Linux Server and I think the Linux Client could need another one or two developers! Just send some email to the mailing list at:

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    6.0: The Team

  • Adam Szalkowski ( He has done all the Windows stuff and he helped me with the Linux Server ...
  • Friedrich Lindenberg ( Linux Server, Website .... (I don't have any ISDN hardware as my old AVM Fritz! doesn't work any more. Would anyone like to donate hardware to a poor OSS developer?)
  • Begumisa Gerald M. ( He's the Linux Client man. *Caution*: that's kernel coding!!!

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    This Site is (C)2002 F. Lindenberg. All trademarks are property of their respective owners and we *do* all love Microsoft. Thanks to for hosting the CAPI20Project. Thanks to Lamafa for supporting me ;)...

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