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The first new Kermit release for Windows in TWENTY YEARS
(and the first free and Open Source version ever)...

  CKW: C-Kermit 10.0 for Microsoft Windows


Download   Install   Run   Export   Coexist   Documentation   Problems   Screenshots

Also see:    CKW How-To   (Ini files, SSH setup, ...)     See daily progress notes 

Frank da Cruz
ckw@kermitproject.org ← questions, problems, reports
Page created: 14 December 2022
CKW Beta date:
Last page update: Mon Sep 25 16:22:54 2023 New York time


• About  • New features  • Problems fixed in   • Download  • Installing  • Running  • Coexistence with K95  • The initialization/customization file  • Exportable to all countries  • Documentation  • Building C-Kermit for IBM OS/2

This page assumes a degree of familiarity with Kermit software; if you need an introduction, look HERE.

The new (2022-23) Open Source release of the Program Formerly Known as Kermit 95 — K95 for short — and which is now called C-Kermit for Windows — CKW for short — draws ever closer to final release, thanks to David Goodwin in New Zealand, who has been working on it since July 2022. His Beta test version is available as of . The previous Windows Kermit version, K95 2.1.3, was released when when Windows ME was current.

CKW Beta test numbers are different from C-Kermit's, which is (as of the same date) , so this one is called C-Kermit for Windows ; it is built using C-Kermit .

OS/2 support... About the same as the previous Beta, when David said "OS/2 status is unchanged — it builds and runs but I've not tried to make any serial connections with it. Network support is currently disabled as I don't know how to build the TCP/IP bits with OpenWatcom yet and leaving NetBIOS enabled causes it to crash on startup for an unknown reason. Might not be too hard for someone who knows what they're doing to get it all going nicely."

By the way, it would also seem to be appropriate to call C-Kermit for Windows "W-Kermit", which looks better than "CKW" in menus like the one at the top of this page, where "C-Kermit for Windows" is too long and "CKW" too short. Also W-Kermit follows the pattern of E-Kermit and G-Kermit, not to mention C-Kermit itself. By the same token, the OS/2 version might be called O-Kermit.


• David's notes  •  What's new in  •  SSH support  •  David's changelog  •  Previous Beta  •  Gallery

About C-Kermit for Windows

Skip ahead to New Features in  ] The CKW Beta announces itself as:
C-Kermit 10.0 Beta.10/Windows-05, Jul  3 2023, for Windows (64-bit)
 Copyright (C) 1985, 2023,
  Trustees of Columbia University in the City of New York.
  Open Source 3-clause BSD license since 2011.
Type ? or HELP for help.
[C:\Users\fdc\] CKW>
The copyright remains with Columbia U, in accordance with the separation agreement of 2011. The LICENSE command shows the new Open Source license. CKW uses the C-Kermit version number, not the old K95 one, which was different (the last K95 release was 2.1.3, which was contemporary with C-Kermit 8.0.207). CKW Beta-test numbers, however, are independent of the C-Kermit ones; for example, CKW Beta 5 is contemporary with (and is based on) C-Kermit 10.0 Beta.10.

Major new features in C-Kermit for Windows

CLICK HERE for a detailed list of new features in .

I hope that CKB's revived support for secure Telnet, FTP, and HTTP connections will encourage the redeployment of secure Telnet and FTP servers around the Internet, since Kermit's client implementations are vastly superior to the SSH regime in power, functionality, flexibility, features, customizability, automatability, and user-friendliness.

C-Kermit for Windows problems fixed in

Known Problems with C-Kermit for Windows Beta

Send bug reports, questions, and comments to ckw@kermitproject.org. or file them in CKW Issue Tracker on GitHub.
  1. If you download a file to CKW whose name contains accented or non-Roman characters (for example "Grüße" in ISO Latin-1 or UTF-8), the file will arrive but its name will be garbled, as (for example) "GrüÃ\237e". This is only the tip of the iceberg. Ever since Day 1, K95's (and CKW's) default TRANSFER CHARACTER-SET has been TRANSPARENT, and its default FILE CHARACTER-SET is LATIN1.

    But Windows supposedly requires that all filenames be encoded as Unicode UTF-16, so any Kermit partner (such as C-Kermit for Unix or VMS) should, in theory, convert both the text-file's name and its contents to UTF-16 when constructing the packets to be sent. This is well and good, but Windows versions have differences and early 32-bit Windows versions didn't support Unicode at all. So how would the Kermit file sender know whether (and how) to encode a non-ASCII filename? (That said, it is still a deficiency of the protocol that it ignores the issue of filename encoding... not to mention length!)

    Windows can't enforce any rule about the encoding of files (or their names) because files can be imported from all different non-Windows OS's in all different encodings. Nobody has ever filed any complaints related to this issue, so I think it's best to let sleeping dogs lie because:

    • Any conceivable change would involve either dangerous assumptions or significant modifications to the Kermit protocol definition;
    • Any change could be an unwelcome surprise to people who depend on the current behavior;
    • Storing text files in Latin-1 encoding on Windows doesn't seem to bother Windows applications like Powershell, Notepad, or Wordpad, which shows them correctly (even though CMD.COM does not).
    • The best advice has always been to use only ASCII characters in filenames (and, for that matter, not put put spaces in them).
  2. The terminal character-set menus (both the dropdown and the "set terminal/file/transfer character-set ?" menus) are a mishmash of official MIME character-set names and made-up pre-MIME "Kermit names" (see THIS TABLE). This is unavavoidable because (a) Kermit predates MIME, and (b) many of the character sets supported by Kermit do not have MIME names. In the menus, all names that are not MIME names for character sets that do have MIME names should also have the corresponding MIME name in the menu; for example "latin1-iso" and "iso-8859-1". Whenever a MIME name exists, it should be accepted but this is not always the case because C-Kermit has so many character-set-name tables: terminal, file, transfer, etc.
  3. In Windows 11 the terminal beep randomly stops working. This is not a problem with CKW, it's a bug in Windows 11. See this page ("Windows 11 application alert sounds go missing after updates") at Microsoft.com. Workaround: "set terminal bell visible".
  4. Also in Windows 11... SSH key exchange works for passwordless SSH connections to hosts that have ancient SSH servers, but for some reason (only on Windows 11) a password popup appears. You don't have to enter a password, you can just hit the Enter key (not Esc!) to make the popup go away, and then key exchange proceeds normally.
  5. In recent Windows versions, apparently half-duplex serial connections regulated by RTS/CTS flow control no longer work. Kermit does not do the flow control itself, it simply tells the serial port device driver which kind of flow control to use. RTS/CTS used to work (e.g. to make a helf-duplex connection to an IBM mainframe through a serial connection to a protocol converter such as the IBM 7171). Since none of this code has been changed in decades, the working theory is that at some point Microsoft reinterpreted RTS to be READY TO RECEIVE rather than REQUEST TO SEND, which would wreck half-duplex connections. Possible workarounds include using CKW on an older Windows version, or C-Kermit on Unix or VMS, or MS-DOS Kermit on a DOS PC.
  6. The maximum for the SET TERMINAL WIDTH command is 256; there's no reason it can't be much larger, especially since CKW's screen can be widened to any width with the mouse, and since modern screens can be extremely wide. If the screen has been stretched to wider than 256, however, SHOW TERMINAL still says its width is 256.
  7. SET TERMINAL HEIGHT has a similar problem: although the screen height can be stretched with mouse, the maximum height for the command is supposedly 79, but SET TERMINAL HEIGHT to (e.g.) 80 or 90 seems to work.
  8. (This one seems to be fixed? It's too soon to know ...)   Sometimes when CKW switches from the terminal screen to the command screen (e.g. when you escape back, when you log out, or when the connection is broken), the CKW prompt is not issued. It is still in command mode, however, and ready to accept commands. If you type the Return or Enter key, you'll get the prompt (but you shouldn't have to).

What are the four dots on the left side of the status line?

They are the VT100 LEDs (lights above its 6, 7, 8, and 9 keys). Host applications can control them by sending escape sequences. To see for yourself, execute this script in C-Kermit on the host while connected to Unix or VMS from CKW:
# Run to see the LEDs; Ctrl-C to stop it.
while true { for i 0 4 1 { xecho \{27}[\m(i)q, sleep 1 } }

To clear the LEDs tell C-Kermit to:

xecho \{27}[0q


C-Kermit for Windows is available as of , downloadable in various configurations from here:


The configurations are:

Package link CPU Architecture Minimum Windows version Description
ckw-b5-x86-64.zip x86-64 Windows XP Service Pack 3 For 64bit PCs. Visual C++ Redistributable: for Windows 7 and newer, or Windows XP SP3 and Vista
ckw-b5-x86-32.zip x86 Windows XP Service Pack 3 For 32bit PCs Visual C++ Redistributable: for Windows 7 and newer, or Windows XP SP3 and Vista
ckw-b5-arm64.zip ARM64 Windows 10 For 64bit ARM devices. No Kerberos/GSSAPI support. Visual C++ Redistributable.
ckw-b5-arm32.zip ARM32 Maybe Windows 8/RT or newer For 32bit ARM devices. It should work on ARM versions of windows older than Windows 10 but this has not been tested. No SSH or Kerberos/GSSAPI support.
ckw-b5-vintage.zip x86 Windows NT 3.51, Windows 95 Feature (and security) reduced for vintage PCs. Visual C++ Redistributable
ckw-b5-nt350.zip x86 Windows NT 3.50 Even more feature reduced for Windows NT 3.50. This may also work for serial connections on Windows NT 3.1. No dialer.
ckw-b5-ia64.zip IA64 (Itanium) Windows Server 2008 R2 For Itanium Workstations and Servers running Windows. Only tested on Server 2008 R2 but may work on older versions. Has SSL/TLS support but no SSH or Kerberos/GSSAPI
ckw-b5-nt350-axp.zip DEC Alpha Windows NT 3.50 Feature-reduced build for NT 3.50 though due to some tools used in the build process it may actually require NT 3.51 or 4.0.
ckw-b5-axp64.zip DEC Alpha 64bit Windows 2000/Whistler For Microsoft-internal 64bit versions of Windows 2000/XP for the Alpha
ckw-b5-src.zip x86, x86-64, ARM64, ARM32, IA64, MIPS, PowerPC, Alpha, Alpha64 Windows NT 3.1, OS/2 Source code. Visual C++ is recommended but it should also work with OpenWatcom 1.9 and MinGW

If you're upgrading from Beta 4, you might want to consult Whats New in Beta 5. If you're upgrading from an earlier release or upgrading from Kermit 95, the full change log and SSH Readme are probably worth a look.

Download procedure

  1. Make a new folder on your desktop named (you can name it whatever you want, but the following instructions refer to ).
  2. Download the desired CKW configuration package from the "Package link" column in Table 1. The appropriate choice for most people (i.e. those using Windows Vista or later) would be .zip, (we'll assume this in the rest of the instructions).
  3. Move (drag) the downloaded zip archive to folder.
  4. Open (double-click) the folder.
  5. Right-click on the .zip file and choose "Extract All...". This creates a subdirectory called (or other suffix, depending on which archive you downloaded). Don't be surprised if there are actually two levels, not just one, e.g. if your directory winds up with a a subdirectory with the same name, which contains the CKW files.
  6. (optional) Delete the .zip file (right-click → delete).


There is (as yet) no "one-click" installer for CKW. Here is the procedure for the current Beta. A distinct advantage of this do-it-yourself method is that, not only can you have CKW and K95 installed at athe same time, you can also have multiple versions of CKW on your PC. Case in point: there is a host that I use on a daily basis that has an antiquated SSH server. The second Beta worked with it, but the third did not because it is built with a newer version of LibSSH, which has dropped support for old SSH servers (this problem was fixed in the 4th Beta). Anway, here is the installation process for the current Beta:
  1. Open the "" folder (double-click it).
  2. The folder contains 46 files, which include:

    • k95g.exe - The executable C-Kermit 10.0 for Windows (K95) program
    • k95.exe - Ditto, but runs in "console mode" (like DOS, not recommended)
    • libcrypto-1_1.dll - Required for SSH
    • ssh.dll - Required for SSH
    • libssl-1_1.dll - Required for SSH
    • And a bunch of others that can be ignored
    The DLL's are required for Kermit to run, so don't delete them.
  3. If you already have an icon on your desktop called "k95g.exe - Shortcut" from the previous CKW test version, rename it (for example to "k95gB4.exe") so you can still have access to to it. Similarly for each CKW Beta you have installed.
  4. In the " folder, Right-click on k95g.exe and choose "Create shortcut" (in Windows 11 you have choose "Show more options" and then choose "Create shortcut"). This creates a file called "k95g.exe - Shortcut" in the same folder.
  5. Drag the "k95g.exe - Shortcut" to your Windows desktop or wherever else you want to run Kermit from. Recommend you rename it to something like CKWB4 so the name doesn't wrap around or get lost on crowded desktops.

Leave the folder as it is; don't move, rename, or delete it, or delete anything that's in it.

The new built-in SSH client is ready to use with password authentication. To set up passwordless key exchange authentication, read these instructions.


Start (run) the new C-Kermit for Windows program by double-clicking the icon you just made in the previous step. The first time you start it you'll get warnings from Windows and/or your antivirus software because this is a new program and it's free and open-source. Examples of warnings:

  1. Windows protected your PC
    Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk.
    More info click this
    App:  k95g.exe
    Publisher:  Unknown publisher
    [ Run anyway ] ← click this
    (see screenshot)
  2. Symantec Endpoint Protection Download Insight
    Our information on this file is inconclusive. We recommend not using this file unless you know it is safe.
    [ Remove this file from my computer ]
    [ Allow this file ] ← click this
    Unproven: There is not enough information about this file to recommend it. Very few users: This file has been seen by fewer than 5 Symantec users. Very new: Symantec has known abou this file approximately 2 days.

    Permission: If you press OK, an application exemption will be created for this file. You should allow only files you are sure are safe. Are you sure you want to allow this file?
    [ Cancel ]
    [ OK ] ← click this
These warnings appear only the first time you start the new CKW. But they come back when you download a new release (and then they go away again after you follow instructions above).

Coexistence with K95 2.1

If you already have Kermit 95 2.1.3 (or earlier) installed on your PC, CKW won't interfere with it and you can use both versions, and you can still use the K95 Dialer. At present CKW is installed in a folder on your desktop, whereas K95 2.1 was installed in the normal Windows way:
Table 2: K95 2.1 directories
File Filename Directory Kermit variable
Executable (GUI) k95g.exe C:\Program Files (x86)\Kermit 95 2.1\ \v(exedir)
Executable (console) k95.exe C:\Program Files (x86)\Kermit 95 2.1\ \v(exedir)
Root startup file k95.ini C:\ProgramData\Kermit 95\ \v(inidir)
Sitewide initialization file k95site.ini C:\ProgramData\Kermit 95\ \v(inidir)
User's customization file k95custom.ini C:\Users\username\AppData\Roaming\Kermit 95\ \v(appdata)
The actual directory names can vary according Windows version, but the variables should always work.

CKW *presently* uses the same initialization and customization files as Kermit 95. If these files contain any commands not supported by CKW or by K95, you can protect them with:

if < \v(version) 1000000 {
    commands for K95    
if >= \v(version) 1000000 {
    commands for CKW
\v(version) is the all-numeric version number of the C-Kermit code used for the Windows build. The last three digits are the edit number. 800207 is C-Kermit 8.0.207 and 1000400 is C-Kermit 10.0 Beta.01. Subsequent Betas have higher numbers, e.g. 1000405. When CKW is finally released it will still peacefully coexist with K95, although the exact mechanisms have yet to be worked out, but most likely all of its file names will start with "ckw" rather than "k95" (as in the table), and it will have its own separate \v(exedir), \v(inidir), and \v(appdata) directories. Or maybe it's best to just keep the k95 prefix.

The CKW Initialization File

More about "Ini files"

In Betas 1 through 4 CKW uses K95's initialization and customization files (Table 2) if they exist. Future Betas might have their own set, e.g. ckwcustom.ini instead of k95custom.ini. Currently, the same directories as for K95 are used for the k95.ini, k95site.ini, and k95custom.ini files. These are plain-text files that contain C-Kermit/K95/CKW commands. The k95custom.ini is where you would set up your preferences. For making connections to other computers, you can define macros for each host that include the access details, the connection and login procedure, and the desired fonts, font-sizes, screen dimensions, colors, position, resize behavior, and so on, for each host you connect to. You can use different attributes (e.g. color) for each host so when you have many connections going at once, you can tell the difference by their distinct appearances, as in this example.

Exportability of SSH client

The US Department of Commerce Bureau of Industry and Security (BIS) Export Administration Regulations (EAR) govern the export of software that includes encryption features. These rules have changed since Kermit 95 was last released in 2003, at which time certain countries were barred from obtaining such software from the USA by mail order, download, or other means. As of 2021, however, Kermit software is no longer subject to export restrictions, and C-Kermit for Windows can include a built-in SSH client based on LibSSH that is, indeed, exportable to all countries. See these references:
  1. Understanding US Export Controls with Open Source Projects, The Linux Foundation
  2. Understanding US Export Controls and Open Source Projects (2021 Update), The Linux Foundation
  3. Publicly Available - Public Domain - Open Source, MIT Office of the Vice President for Research
  4. Bureau of Industry and Security Export Administration Regulations, US Department of Commerce (2022)
  5. Bureau of Industry and Security Commerce Control List Category 5 - Telecommunications and Information Security

In brief (paraphrasing from item 5):  Publicly available ready-to-use software whose primary function is other than information security, that includes an openly available encryption component without modifications, and that is of interest to a wide range of individuals and businesses, is exempt from the BIS Export Administration Regulations. That's why LibSSH and numerous SSH clients are downloadable on the Internet by anybody at all, no matter what country they are in. CKW will be no different.

Similar considerations apply to Kermit's built-in OpenSSL and Kerberos 5 features, such as its Telnet, FTP, and HTTP clients.


Specific to C-Kermit for Windows:
A "How To" document for getting started with CKW:

David Goodwin's notes:

Since C-Kermit for Windows is C-Kermit, you can refer to the C-Kermit documentation for most everything else:
For an introduction to the Kermit scripting language (which lets you write procedures to automate common tasks), see this page:
For CKW's Windows-specific aspects, see:
  1. Chapter 6 of the Kermit 95 manual: Using the Command Screen,
  2. Chapter 7 of the Kermit 95 manual: Using the Terminal Emulator, and
  3. Chapter 8 of the Kermit 95 manual: File Transfer.

Building C-Kermit for IBM OS/2

David was asked in September 2023 how to build C-Kermit 10 for OS/2; the rest of this section is his response.

the OS/2 and Windows versions descend from Kermit 95 and share a fair bit of code and so are both developed in the same repository over on github here: https://github.com/davidrg/ckwin/.

The 32bit OS/2 version of Kermit 95 2.1.2 was built with some version of IBMs VisualAge C++ compiler but I don't have a license for that so I use OpenWatcom 1.9 at the moment. As no one has run the code through VisualAge C++ in over 20 years I wouldn't be surprised if there were a few build errors at this point.

With OpenWatcom 1.9 you can build either directly on OS/2, or cross-compile from Windows. Instructions for building it are here: https://github.com/davidrg/ckwin/blob/master/doc/os2-building.md. Github Actions also automatically produces 32bit OS/2 binaries which are available as the "ckos2-ow1.9-x86" artifact on any recent build.

When built with OpenWatcom 1.9 there are a number of bugs that currently impact its usability though, documented here: https://github.com/davidrg/ckwin/issues?q=is%3Aissue+is%3Aopen+label%3AOS%2F2+label%3Abug. At this stage I don't know if these are a result of switching compilers (and so wouldn't exist/be visible when built with VisualAge C++) or if they're a result of going 20 years without maintenance. Probably a mix of both.

There is still at least some code present for 16bit OS/2 (1.x) but it's not been supported since C-Kermit 5A(190) of October 1994 so it's probably some way from being buildable at this point.

As for Windows, this page covers supported compilers and which ones are required for various features: https://github.com/davidrg/ckwin/blob/master/doc/compilers.md.

Build instructions for Visual C++ and OpenWatcom are here: https://github.com/davidrg/ckwin/blob/master/doc/building.md, and for MinGW: https://github.com/davidrg/ckwin/blob/master/doc/mingw-building.md.

Choice of compiler is mostly down to target windows version and CPU architecture. With the right compiler, C-Kermit for Windows will run on every 32bit or 64bit non-embedded/mobile version of Windows except for NT 3.10 (it does run there but there are issues — https://github.com/davidrg/ckwin/issues/164), and on all CPU architectures windows has officially supported (x86, x86-64, MIPS, Alpha, PowerPC, Itanium, ARM, ARM64) as well as the never released 64bit Windows for the Alpha.

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