Feature Comparison - davidrg/ckwin GitHub Wiki

This page provides quick comparison of Kermit 95 with other open-source terminal emulators for Windows. Most of this information has been taken from the following locations:

• https://en.wikipedia.org/wiki/Comparison_of_SSH_clients
• https://ttssh2.osdn.jp/manual/4/en/
• https://www.chiark.greenend.org.uk/~sgtatham/putty/

If you see something on here that isn't correct (or something you think shouldn't be left out) please correct it or raise it over on github discussions so it can be corrected! It isn't helpful to anyone if some part of this page is incorrect or misleading.

Connection Protocols

Virtual Terminal connections over the following protocols/connection types:

Feature	Kermit 95	TeraTerm	PuTTY
Serial	✅	✅	✅
RFC2217 Serial over Telnet	✅	❌	❌
SSH v1	❌	✅	✅
SSH v2	✅ (XP SP3+)	✅	✅
Telnet	✅	✅	✅
Telnet-SSL	✅ (XP SP3+)	❔	❔
RLogin	✅	❌	✅
Named Pipe	✅	✅	✅
NetBIOS	✅ (OS/2 only)	❌	❌
PTY	✅ (Windows 10 v1809+)	❌	✅ (pterm)
Cygwin	❌ †	✅	❌
CTERM	✅ (Requires Pathworks32)	❌	❌
LAT	✅ (Requires Pathworks32)	❌	❌
Modem	✅ TAPI, RFC2217, built-in	❌	❌
DLL	✅ ‡	❔	❔
SUPDUP	❌	❌	✅

For more details on supported telnet options, see Telnet Options further down this page

† While Kermit 95 has no specific support for Cygwin, you can access the Cygwin console via a PTY on sufficiently new versions of Windows. PTYs on Windows do come with some limitations though so it's not a true replacement for proper Cygwin support. You can open a Cygwin session in K95 with a command such as pty cmd /c C:\\cygwin64\\cygwin.bat

‡ K95 can make connections via a user-supplied/written DLL allowing support for other protocols not built-in.

IP Connections Types

IP connections (SSH, Telnet, etc) can be made via the following methods:

Feature	Kermit 95	TeraTerm	PuTTY
IPv4	✅	✅	✅
IPv6	❌ † #224	✅	✅
SOCKS 4/5 Proxy	❌ ‡ #78	✅	✅
HTTP Proxy	❌ ‡ #78	✅	✅
Telnet Proxy	❌	✅	✅

† IPv6 is only usable SSH connections

‡ Note that K95 does support HTTP and SOCKS proxy connections for telnet and RLogin, proxies are only unsupported for SSH.

Forwarding

Feature	Kermit 95	TeraTerm	PuTTY
X11 over SSH	✅	✅	✅
X11 over Telnet	✅	❌	❌
Port forwarding over SSH	✅	✅	✅
Dynamic forwarding over SSH	❌ #297	✅	✅

File Transfer

Protocol	Kermit 95	TeraTerm	PuTTY
Kermit	✅ Complete implementation including server support	✅ limited †	❌
IKS Server	✅	❌	❌
X-MODEM	✅	✅	❌
Y-MODEM	✅	✅	❌
Z-MODEM	✅	✅	❌
B-PLUS	❌	✅	❌
Quick-VAN	❌	✅	❌
FTP	✅	❌	❌
FTPS	✅ (XP SP3+)	❌	❌
HTTP	✅	❌	❌
HTTPS	✅ (XP SP3+)	❌	❌
SFTP	❌ #219	✅	✅
SCP	❌	✅	✅
None ‡	✅	✅	❌

† Tera Terms Kermit implementation is fairly limited lacking support for server mode or network connections, and appears to have only very limited protocol options.

‡ Transmit a file as though it were typed in to the keyboard. Both TeraTerm (File -> Send file) and Kermit 95 (the transmit command, configured via the set transmit commands) support doing this, optionally with a delay between each line or character.

Platform Support

The platforms supported by the latest stable release only. Note that Kermit 95s beta releases are stable releases for all intents and purposes - the last proper stable release was in 2003 and isn't freely redistributable. Kermit 95 3.0 will likely loose the beta tag once the features that went missing in its open-sourcing have been added back in.

Feature	Kermit 95	TeraTerm	PuTTY
Version	Kermit 95 3.0 beta 7 (27 January 2025)	Tera Term 5.3 (8 September 2024)	PuTTY 0.83 (28 February 2025)
Minimum Windows Version	NT 3.50, 95 (SSH and Secure Telnet require XP SP3 or newer)	v5.3 needs at least Windows Vista (Windows XP gives "Not a valid Win32 application")	Windows XP (Windows 2000 and older produce "Not a valid win32 application"). 3rd-party (not always up-to-date) builds exist for older Windows versions not officially supported, including Win32s.
Native x86-64 Windows support	✅	❌ not supported but can apparently be built from source	✅
Native ARM64 Windows support	✅	❌	✅
Native ARM32 Windows support	✅	❌	✅
Other Windows Architectures	Alpha, MIPS, PowerPC, Alpha64 and Itanium (all without SSH support)	none	none officially, but 3rd party builds (not always up to date) exist
Minimum OS/2 Version	OS/2 2.0 with IBM TCP/IP 2.0 (optional)	❌	❌ QPutty exists but is a decade out of date
Linux/Unix Support	C-Kermit provides most of K95s features, but without terminal emulation (you run it inside one, like xterm) or a built-in SSH client (wraps openssh)	❌	✅

Terminal Emulation

Feature	Kermit 95	TeraTerm	PuTTY
Mouse Input	✅	✅	✅
256 colors	❌ #194 - coming in the next release (beta 8)	✅	✅
24-bit color	❌ #220 - coming in the next release (beta 8)	❌	✅
Bracketed Paste	✅	✅	✅
Alternate Screen Buffer	❌ #231	✅	✅
OSC 8 Hyperlinks	❌ #123 - an equivalent private escape sequence is supported however	❌	❌ not supported
Clickable URLs	✅	❔	❌ not supported
Unicode	✅ Plane 0 only, #315 for other planes	✅	✅
PCTERM Keyboard Mode	✅	❌	❌
SGR Bold Attribute	✅ as bold font, bright color, bold font+bright color, or specific color	✅ As font and/or color	✅ Bold font, or ANSI color (or both)
SGR Dim Attribute	✅ same as bold, or a specific (dim by default) color	❌ Unsupported	✅
SGR Blink Attribute	✅ as blinking text (default), or specific color	❌ As color only	✅ As color by default, blink option under terminal settings
SGR Italic Attribute	✅ as italic font, or specific color	❌ Unsupported	❌ Unsupported
SGR Underline Attribute	✅ as underlined font, or specific color	✅ as font and/or color	✅
SGR Attributes as Colours	✅ for normal, blink, dim, italic, reverse, underline.	✅ For normal, bold, blink, reverse, url, underline	❌ not supported (except for bold)

Kermit 95

Kermit 95 provides a fairly complete implementation of DECs VT52, VT100, VT102, VT220 and VT320 with colour and mouse extensions, double width and double-height characters, dim characters, italics and underlining. Multiple pages, soft-characters, sixels and ReGIS are not supported at this time.

In addition to the industry standard VT series of terminals, Kermit 95 emulates a wide selection of other terminals including ANSI-BBS; Avatar/0+; AT386; BeBox ANSI; Data General DASHER D200, D210; Data General DASHER D217 in native and Unix modes; Hazeltine 1500; Heath/Zenith 19; Hewlett Packard 2621A; HPTERM; IBM HFT and AIXTERM; IBM 3151; Linux console; Microsoft VTNT; QNX ANSI and QNX Console; SCOANSI; Siemens Nixdorf BA80 and 97801-5xx; Sun Console; Televideo TVI910+, TVI925, TVI950; Volker Craig VC404; Wyse 30, 50, 60, 160, and 370

For more details on the emulation profiles, see this page: https://davidrg.github.io/ckwin/current/termtype.html

TeraTerm

"VT100 emulation and selected VT200/300 emulation", Tektronix 4010

Based on the available documentation, it also implements a selection of VT420 and xterm features: https://teratermproject.github.io/manual/5/en/about/ctrlseq.html

PuTTY

"an xterm terminal emulator", though it should be noted that its emulation does have known bugs and it is missing a substantial number of control sequences and parameters compared to Kermit 95 and TeraTerm.

Other Features

Feature	Kermit 95	TeraTerm	PuTTY
Initial Release	July 2011 (as open source), November 1995 (as Kermit 95), July 1988 (as OS/2 C-Kermit)	2004 (as TeraTerm), 1994 (as TeraTerm Pro)	January 1999
Scripting	✅ C-Kermit, REXX (OS/2 and XP+ on x86/x86-64)	✅ "Tera Term Language"	❌ not supported
Keyboard Mapping	✅	✅	❌ not-supported
Session Tabs	❌	✅	❌
Find Text in Scrollback	✅	❌	❌
Bookmarks in Scrollback	✅	❌	❌
Log Replaying	✅ †	✅ ^	❌
Duplicate Session	❌	✅	✅
Optional menubar, toolbar and statusbar	✅	✅	❌
Remote access via network or dial-in	✅ ‡	❌	❌
stdin/stdout for automation/scripting	✅	❌	✅ (plink.exe)
Kerberos Authentication	✅ For SSH, Telnet, Rlogin, IKS and FTP. Requires MIT Kerberos for Windows	❌	✅
GUI	✅ Windows only, not on NT 3.50 for Alpha/MIPS	✅	✅
TUI/CLI (runs in a Windows console window)	✅ With some limitations to its terminal emulation (eg, no double width/height characters, underlining, etc)	❌	✅ with no terminal emulation
Configurable per-character delay	✅ for any connection type: set output pacing	✅ For serial only, per character or per line	❌ not supported
GUI Authentication Dialogs	✅ optional	✅	❌ not supported
Keyboard shortcuts for select & copy	✅	❔	❌ not supported
Execute Local Command requested by host	✅ APC - off by default for obvious security reasons, can be limited to "safe" commands only if you trust the host	❌	❌ not supported

† Based on the TeraTerm documentation it sounds like the "log replay" function effectively just writes the log file out to the terminal emulator which will interpret any escape sequences it contains. The following commands in K95 should achieve the same effect:

SET TERMINAL TYPE VT320   ; Or any other supported terminal type
SET INPUT PACING 50       ; How many miliseconds to pause between each character
SET NETWORK TYPE FILE     ; Connect to a file
SET HOST SESSION.LOG      ; set the filename
CONNECT                   ; connect

If you find yourself doing this often, you could define a macro allowing you to do the job with a single command - log_replay session.log:

def log_reply {
  SET TERMINAL TYPE VT320   ; Or any other supported terminal type
  SET INPUT PACING 50       ; How many miliseconds to pause between each character
  SET NETWORK TYPE FILE     ; Connect to a file
  SET HOST \%1              ; set the filename
  CONNECT                   ; connect
}

‡ Kermit 95 can listen for incoming network or modem connections for remote access. Hostmode, a BBS-like kermit script, is an example of this.

Telnet Options

Contrary to popular opinion, telnet is not equivalent to a raw TCP socket. The telnet protocol supports a large number of options which must be negotiated between the client and server during connection establishment. The table below documents the options supported by one or more of the programs in this comparison. For more information on Telnet support in Kermit 95, see Kermit 95 Telnet Reference. Supported options in PuTTY and Tera Term are from inspecting the code (on 2025-03-03) as their documentation does not explicitly state what is supported. For a list of all possible Telnet options, see Telnet Options at IANA.

Option	Name	RFCs	Kermit 95	TeraTerm	PuTTY
0	Binary	RFC856	✅	✅	✅
1	Echo	RFC857	✅	✅	✅
3	Suppress Go Ahead	RFC858	✅	✅	✅
18	Logout	RFC727	✅	❌	❌
23	Send Location	RFC779	✅	❌	❌
24	Terminal Type	RFC1091	✅ †	✅	✅
31	NAWS	RFC1073	✅	✅	✅
32	Terminal Speed	RFC1079	❌	✅	✅
35	X Display Location	RFC1096	✅	❌	❌
36	Environment Option	RFC1408	❌	❌	✅
37	Authentication	RFC2941	✅ ‡	❌	❌
38	Encryption	RFC2946	✅ §	❌	❌
39	New Environment	RFC1572	✅	❌	✅
44	Com Port Control	RFC2217	✅	❌	❌
46	START TLS	Internet Draft	✅	❌	❌
47	KERMIT	RFC2840	✅	❌	❌
49	Forward X	Internet Draft	✅	❌	❌
138	Pragma Logon¶	None/Proprietary	✅	❌	❌
139	Pragma SSP Logon¶	None/Proprietary	✅	❌	❌
140	Pragma Heartbeat¶	None/Proprietary	✅	❌	❌
200	IBM SAK ††	None?	✅	❌	❌

† As PuTTY and Tera Term only emulate a single terminal type, they simply report their terminal type to the remote host. Kermit 95 supports many terminal types, so if the telnet server doesn't like the currently chosen terminal type, Kermit 95 will keep trying different terminal types until it lands on one the server supports. The OpenVMS telnet server is one example of a telnet server that may actually reject a chosen terminal type causing Kermit 95 to switch to another.

‡ Kermit 95 supports Kerberos V authentication on modern Windows hosts if MIT Kerberos for Windows is installed. It can optionally be built from source with Kerberos IV and SRP authentication (requires obsolete/unmaintained libraries).

§ Kermit 95 supports all (now quite obsolete) encryption types listed in the RFC: CAST128_CFB64, CAST128_OFB64, CAST5_40_CFB64, CAST5_40_OFB64, DES3_CFB64, DES3_OFB64, DES_CFB64 and DES_OFB64.

¶ Commands to configure these Pragma Systems Telnet Server proprietary telnet options (eg, set telopt pragma-logon) are currently hidden, and show telopt does not show these options. They were added for Kermit 95 v2.2 (never released) and have likely not been tested since then.

†† Another hidden telnet option, this is for IBMs Secure Attention Key. For use with the \Ktn_sak kverb.