Authors:
Bill Catchings, Bob Cattani, Chris Maio, Columbia University
Modified from UNIX Kermit to Os9 Kermit By Glean Seaton and
Robert
A. Larson
with fixes and contributions from many others.
Documentation:
Walter Underwood, Ford Aerospace (Palo Alto, CA)
Changed for Os9 Kermit by Robert A. Larson
Version:
1.5
Date:
July 1985
A sample, working implementation of the Kermit "kernel" was written in
the C
language, and widely distributed in the Kermit Protocol Manual.
This
kernel
was intended merely to illustrate the protocol, and did not include a
"user
interface", nor some of the fancy features like server support, 8-bit
quoting,
file warning, timeouts, etc. Several sites have added the necessary
trappings
to make this a production version of Kermit, usually under the UNIX
operating
system. Limited server functions have also been added to the Os9
version.
The keyword style of user/program interaction favored by Kermit (program
types
prompt, user types command followed by operands, program types another
prompt,
etc) is contrary to the UNIX style, so UNIX implementations have a
style more
familiar to UNIX users. The Os9 version has retained this style of
command
interface.
C versions of Kermit are running successfully on VAX and
PDP-11
UNIX systems, IBM 370-compatible mainframes under Amdahl UTS, and
the SUN
Microsystems MC68000-based and other workstations.
There is a new version of Kermit written in C called C-Kermit. (The
current
version as of July 1985 is 4c.) It is recommended for Unix and
adapting to
other operating systems if memory is adiquate.
(It is being
adapted to
Os9/68000, but is probably to large for Os9/6809.)
Os9 filespecs are of the form
dir1/dir2/dir3/ ... /filename
where the tokens delimited by slashes form a path name, and are each
limited to
29 characters in length. The final token in a path is the actual file
name.
By convention, it is of the form name.type, but there is nothing special
about
the dot separating name and type; to Os9 it's just another character, and
there
may be many dots in a filename.
In the tradition of UNIX, here's the Os9 KERMIT "man page".
NAME
kermit - file transfer, virtual terminal over tty link
SYNOPSIS
kermit cl[e] line [esc]
kermit r[ddifl] [line]
kermit s[ddifl] [line] file ...
kermit gl[ddif] line file ...
2
kermit ql[ddif] line
kermit h[ddifl] [line]
DESCRIPTION
virtual
Kermit provides reliable file transfer
terminal
communication
between
and
primitive
machines.
It
has
been
implemented
on
many
different
computers,
including
microprocessors
(see
below).
The
files transferred
may be
arbitrary ASCII data (7-bit
of
characters)
and
may
be
any
length.
The file transfer protocol uses small (96
character)
check summed packets, with
ACK/NACK
responses
and
timeouts.
Os9 Kermit by defaults (changeable by compilation
options) uses
a fifteen "second" timeout and ten retries.
The arguments to kermit are a set of flags (no
spaces
between
the flags), three optional args (which, if included, must
be in
the same order as the flags
which
indicate
their
presence),
and,
if
this is a Send or Get operation a list of one
or more
files.
Kermit has six modes, Connect, Send, Receive,
Quit,
Get,
and
Host.
Connect is for a virtual terminal connection,
Send and
Receive may be used to transfer files
in
a
non-server
mode,
Send,
Get,
and Quit are used with a remote kermit
server, and
Host is used to make the Os9 system a
server
itself.
These
modes are specified by the first flag, which should be c,
s, r,
g, q, or h respectively.
Exactly one mode must be
specified.
The d flag (debug) makes kermit a bit more verbose.
The
states
kermit
of its
goes through are printed along with other traces
operation.
A second, third, and even fourth d flag will
cause
kermit to give an even more detailed trace.
The i flag (image) allows slightly more efficient file
transfer
run
between Os9 machines.
Normally (on Kermits defined to
Os9
is
on
systems)
return
mapped
to
CRLF on output,
LF's are
discarded on input, and bytes are masked to 7 bits.
If
this is
set,
no mapping is done on returns, and all eight bits
of each
byte are sent or received.
The l flag (line) specifies the tty line that kermit
should use
to
communicate with the other machine.
This is
specified as a
regular filename, like "/t2".
If no
l
option
is
specified,
standard
input is used and kermit assumes it is running
on the
remote host (i.e.. NOT the machine to which
terminal
your
is
attached).
The
e flag (escape) allows the user to set the first
character
of the two character escape sequence for Connect
mode.
When
the escape character is typed, kermit will hold it and
wait for
the next character.
If the next character is c
or
C,
kermit
will
second
close the connection with the remote host.
If the
3
character is the same
as
the
escape
character,
the
escape
character
itself
is passed.
An exclamation mark ('!')
as the
second character will cause shell to be forked.
your
(Use
EOF
character to return to the kermit connect mode.)
Any
character
other than these two results in a bell being sent to the
user's
terminal
host.
and
no
characters
passed
to the remote
All
other typed characters
are
passed
through
unchanged.
tilde ('~').
(Control-3
The
default
escape
character
is
on the
standard Coco keyboard.)
The file arguments are only meaningful to a Send or Get
kermit.
The
Receiving
kermit
will attempt to store the file
with the
same name that was used to
send
it.
Os9
kermits
normally
convert
outgoing
file names to uppercase and incoming
ones to
lower case (see the f flag).
If a filename
contains
a
slash
(/) all outgoing kermits will strip off the leading part
of the
name through the last slash.
In
the
Get
command,
filenames
will
be
sent
to the remote host as is and the
filenames sent
back will
be
converted
as
usual
for
a
receiving
kermit.
(Wildcard characters may be expanded on the remote end.)
The
Quit
command
will
send a "Generic Finish" packet
to the
remote kermit server.
The Host command has not been fully implemented and
tested
as
of this writing.
EXAMPLE
We are
For
this
example
we
will
assume
two Os9 machines.
logged onto "Os9a" (the local machine), and want to
communicate
with "Os9b" (the remote machine).
There is a modem on
"/t2".
We
want
to
connect
to "Os9b", then transfer "file1"
to that
machine.
We type:
kermit cl /t2
Kermit answers:
Kermit: connected...
Now we dial the remote machine and connect the modem.
Anything
typed
on
the
terminal will be sent to the remote
machine and
any output from that machine will be displayed on our
terminal.
We hit RETURN, get a "login:" prompt and login.
Now
we need to start a kermit on the remote machine so
that we
can send the file over.
First we start up the remote,
(in this
case
receiving)
kermit,
then
the
local,
one.
Remember that we are talking to Os9b right now.
(sending)
4
We type:
kermit r
(there is now a Receive kermit on Os9b)
We type ~ (the escape character) and then the letter c to
kill
the local (Connecting) kermit:
~c
Kermit answers:
Kermit: disconnected.
We type:
kermit sl /t2 file1
Kermit answers:
Sending file1 as FILE1
When
the
transmission
is
finished,
kermit will type
either
"Send complete", or "Send failed.", depending on the
success of
the
transfer.
If we now wanted to transfer a file
from os9b
(remote) to os9a (local), we would use these commands:
kermit cl /t2
(connected to Os9b)
kermit s file9
~c (talking to Os9a again)
kermit rl /t2
After all the transfers were done, we should connect
again, log
off of Os9b, kill the Connect kermit and hang up the
phone.
FEATURES
Kermit can interact strangely with the tty driver.
The
KERMIT
Protocol
uses
only
printing
ASCII
characters,
Ctrl-A, and CRLF.
Ctrl-S/Ctrl-Q
flow
control
can
used
"underneath"
the
Kermit
currently
implemented in Os9 Kermit.
protocol,
but
is
not
be
Since BREAK is not an ASCII character,
send
kermit
cannot
a
BREAK
to the remote machine.
On some systems, a BREAK
will be
read as a NUL.
This kermit does have timeouts
so
when
run
under
Os9,
the
protocol is stable when communicating with "dumb" kermits
(that
don't have timeouts).
DIAGNOSTICS
had
the
cannot open device
The file named in the line argument did not exist
or
5
wrong permissions.
Could not create file
A Receive kermit could not create the file being sent to
it.
nothing to connect to
A Connect kermit was started without a line argument.