Kermit FAQ

These are frequently asked questions about Kermit and C-Kermit.

What is C-Kermit and how does it differ from Kermit?

C-Kermit is a communications package. It has a text UI, a portable scripting language (similar in concept to the shell, but with built-in screen-scraping automation like expect and built-in file transfer), an implementation of the Kermit file transfer protocol protocol, network client and server, serial port interface, BBS client, and more. Kermit runs on hundreds of platforms, from the long-dead computers of the 1970s, pocket calculators of the 1990s, and modern desktop and mobile OSs.

I need to emphasize here the difference between the Kermit protocol and the C-Kermit software. The protocol is primarily used for transferring files, but also in the more sophisticated implementations such as C-Kermit, can be used to perform actions on the remote such as renaming files, creating directories, and so forth. C-Kermit is an implementation of the protocol, but also adds a lot of other features, such as a scripting language and X/Y/ZModem support.

C-Kermit is either directly or indirectly the modern, actively-maintained Kermit implementation. A fork of C-Kermit, ckwin, adds a GUI for OS/2 and both modern and historic Windows. To obtain C-Kermit or ckwin, see downloads.

How does Open Kermit relate to the Kermit Project?

A more detailed treatment of this topic is available in history.

In 1981, the Kermit project began at Columbia University, and they eventually supported and funded it. They continued this support until 2011. During this time, the source to C-Kermit was available, but not under an Open Source license.

In 2011, Columbia ended their support of Kermit, but open-sourced their software. Frank da Cruz, who had worked on Kermit at Columbia since the beginning, created the Kermit Project as a volunteer, continuing development of Kermit outside Columbia.

In 2025, Frank retired from the Kermit Project, and no releases have been made since.

John Goerzen, who had been involved maintaining Kermit on Debian, created the Open Kermit project to continue C-Kermit and support its modern evolution. He had previously been maintaining and distributing security patches to distributions, and this was getting unwieldy. The modern evolution included writing a test suite, proper CI, compatibility fixes for modern platforms, hosting on Github, and a website (this one) that is easy for a community to maintain. You can see all the work for C-Kermit 11 in the changelog.

Both Columbia and Kermit Project’s websites continue to be operational. With Frank’s permission, John also operates mirrors of the Columbia and Kermit Project at https://kermit.mirrors.quux.org/, recognizing the significant value of the information contained therein.

What’s up with the C-Kermit version numbers?

During and after the transition from Columbia, Frank made releases variously identified as 9.x dev, 9.x alpha, 10.x beta, etc. were created. The last “official” (not alpha, beta, or dev) kermit release prior to 11.0 was 9.0.302 of July 2011 (commit 0fd869b4).

Due to the potentially-confusing history of 9.x and 10.x numbering, I opted to just start fresh at 11.0. This also is an accurate indication that there was major work done in 11.0; it’s not just the last 10.x beta rebadged.

The changelog also contains a summary of all the work done in the 9.x and 10.x series since 9.0.302.

Is the command-line interface derived from DOS?

No. The first Kermit implementation was for TOPS-20, and that inspired the Kermit interface. TOPS-20 also inspired OpenVMS, CP/M, and DOS, which in turn carried on into Windows.

In particular, C-Kermit’s CLI is much more powerful than DOS ever had, and its scripting language is more akin to a full-featured Unix shell than a DOS batch file.

C-Kermit primarily runs on Unix these days, and you can also see plenty of Unix mannerisms in it also.

If you think of it like a -- long option in Unix is similar to a / option in Kermit, you’ll be set.

What platforms does Kermit run on?

Pretty much every single one you’ve ever heard of, plus a bunch you haven’t.

The tier 1 platforms for C-Kermit, which receive CI support and auto-built binaries for each release, are Linux, MacOS, FreeBSD, NetBSD, and OpenBSD. ckwin additionally supports 32-bit OS/2 and 32- and 64-bit Windows. C-Kermit contains code to support many other Unix flavors, plus some non-Unix OSs like VMS. While every effort is made to preserve compatibility during development, these systems aren’t readily available in CI and therefore aren’t automatically tested. (This is, however, the state of affairs C-Kermit was in for decades, so it’s not a regression.)

Hundreds of additional platforms have been supported by C-Kermit as well as other codebases over the years.

There have been plenty of other Kermit implementations besides C-Kermit. For instance, Kermit 20 was the first Kermit implementation, and it was for the TOPS-20 operating system, which was introduced in 1976 and ended in 1988. The last Kermit release for it was made in 2024! You can probably find Kermit for your favorite old Unix or Micro; it’s there for Commodore 64, for IBM mainframes, Android phones, just about anything.

The getting Kermit page can direct you to downloads for everything, old and new.

Where is there more information?

See the documentation page.

Where can I get help, submit a bug report, or discuss Kermit?

See the support page.

Where can I get the source code? Can I contribute?

See the getting Kermit page for software. For the source code to this website, see about this site.

Contributions are welcome! Both of the links above will direct you to the appropriate Github project to send pull requests.

Is Kermit slow? Can I speed it up?

The original Kermit protocol used small packet sizes (less than 100 bytes) and was compatible with links that weren’t 8-bit clean. Modern Kermit supports packets up to roughly 9KB, sliding windows, and streaming mode (which requires no ACKs at all). If you are experiencing slow transfers, chances are the other end is ancient, or you need to do some tuning.

What about G-Kermit and E-Kermit?

G-Kermit was released in 1995 under the GNU GPL Open Source license. It is a small, command-line-only program, with no scripting language, no interactive interface (like C-Kermit’s internal CLI), etc. Part of the reason for its existence was to provide software that could be freely used (C-Kermit’s license at the time caused trouble for some, including Linux distributions). Another goal was to make a smaller Kermit.

The Open Sourcing of C-Kermit in 2011 and the increased capabilities of today’s hardware means that C-Kermit needs very few resources by modern standards and there is no need for an Open Source Kermit program beyond C-Kermit. G-Kermit received one update, in 2021, which adapted it for more modern C compilers, header files, and libraries. However, it has been effectively unmaintained since 1995 and is probably not suited to today’s modern systems. Nevertheless, it remains included in a number of Linux distributions and BSD port trees.

E-Kermit was designed for use in embedded devices, firmware, and so forth. It is not actively maintained, but likely remains useful for the purpose. For more information, see https://www.kermitproject.org/ek.html.

I’m having weird problems on NetBSD

See the note in platform-specific notes.

Older questions

The older Kermit Project also has a FAQ; see https://www.kermitproject.org/ckfaq.html.