Title: Transfer your files with Kermit

	Title: Transfer your files with Kermit
	Author: Solène
	Date: 31 January 2019
	Tags: unix kermit
	Description:

	Hi, it's been long time I wanted to write this article. The topic is
	Kermit,
	which is a file transfer protocol from the 80's which solved problems
	of that
	era (text files and binaries files, poor lines, high latency etc..).

	There is a comm/kermit package on OpenBSD and I am going to show you
	how to use
	it. The package is the program ckermit which is a client/server for
	kermit.

	Kermit is a lot of things, there is a protocol, but it's also the
	client/server, when you type kermit, it opens a kermit shell,
	where you
	can type commands or write kermit scripts. This allows scripts to be
	done using
	a kermit in the shebang.

	I personally use kermit over ssh to retrieve files from my remote
	server, this
	requires kermit on both machines. My script is the following:

	#!/usr/local/bin/kermit +
	set host /pty ssh -t -e none -l solene perso.pw kermit
	remote cd /home/ftp/
	cd /home/solene/Downloads/
	reget /recursive /delete .
	close
	exit

	This connects to the remote server and starts kermit. It changes the
	current
	directory on the remote server into /home/ftp and locally it goes
	into
	/home/solene/Downloads, then, it start retrieving data, continuing
	previous
	transfer if not finished (reget command), for every file finished, it's
	deleted
	on the remote server. Once finished, it close the ssh connection and
	exits.

	The transfer interfaces looks like this. It shows how you are
	connected, which
	file is currently transferring, its size, the percent done (0% in the
	example),
	time left, speed and some others information.

	C-Kermit 9.0.302 OPEN SOURCE:, 20 Aug 2011, solene.perso.local
	[192.168.43.56]

	Network Host: ssh -t -e none -l solene perso.pw kermit
	(UNIX)
	Network Type: TCP/IP
	Parity: none
	RTT/Timeout: 01 / 03
	RECEIVING: src.tar.gz => src.tar.gz => src.tar.gz
	File Type: BINARY
	File Size: 183640885
	Percent Done:

	...10...20...30...40...50...60...70...80...90..100
	Estimated Time Left: 00:43:32
	Transfer Rate, CPS: 70098
	Window Slots: 1 of 30
	Packet Type: D
	Packet Count: 214
	Packet Length: 3998
	Error Count: 0
	Last Error:
	Last Message:

	E to send Error packet, ^C to quit immediately, ^L to refresh
	screen.


	What's interesting is that you can skip a file by pressing "X", kermit
	will
	stop the downloading (but keep the file for later resuming) and start
	downloading the next file. It can be useful sometimes when you transfer
	a bunch
	of files, and it's really big and you don't want it now and don't want
	to type
	the command by hand, just "X" and it skips it. Z or E will exists the
	transfer
	and close the connection.


	Speed can be improved by adding the following lines before the reget
	command:

	set reliable
	set window 32
	set receive packet-length 9024

	This improves performance because nowadays our networks are mostly
	reliable and
	fast. Kermit was designed at a time when serial line was used to
	transfer data.
	It's also reported that Kermit is in use in the ISS (International
	Space
	Station), I can't verify if it's still in use there.

	I never had any issue while transferring, even by getting a file by
	resuming it
	so many times or using a poor 4G hot-spot with 20s of latency.

	I did some tests and I get same performances than rsync over the
	Internet, it's
	a bit slower over Lan though.

	I only described an use case. Scripts can be made, there are a lot of
	others
	commands. You can type "help" in the kermit shell to get some hints for
	more
	help, "?" will display the command list.

	It can be used interactively, you can queue files by using "add" to
	create a
	send-list, and then proceed to transfer the queue.

	Another way to use it is to start the local kermit shell, then type
	"ssh
	user@remote-server" which will ssh into a remote box. Then you can type
	"kermit" and type kermit commands, this make a link between your local
	kermit
	and the remote one. You can go back to the local kermit by typing
	"Ctrl+\",
	and go back to the remote by entering the command "C".

	This is a piece of software I found by lurking into the ports tree for
	discovering new software and I felt in love with it. It's __really__
	reliable.

	It does a different job compared to rsync, I don't think it can
	preserve time,
	permissions etc... but it can be scripted completely, using parameters,
	and
	it's an awesome piece of software!

	It should support HTTP, HTTPS and ftp transfers too, as a client, but I
	did not
	get it work. On OpenBSD, the HTTPS support is disabled, it requires
	some work
	to switch to libreSSL.

	You can find information on the [official
	website](http://www.kermitproject.org).