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CKCKER.BWR "Beware File" for C-Kermit Version 5A -*- text -*-
Applies to 5A(189)
Last update: Sat Nov 20 15:49:04 1993
Authors: Frank da Cruz, Christine M. Gianone, Columbia University.
Copyright (C) 1985, 1993, Trustees of Columbia University in the City of New
York. The C-Kermit software may not be, in whole or in part, licensed or
sold for profit as a software product itself, nor may it be included in or
distributed with commercial products or otherwise distributed by commercial
concerns to their clients or customers without written permission of the
Office of Kermit Development and Distribution, Columbia University. This
copyright notice must not be removed, altered, or obscured.
Report problems, suggestions, fixes, etc, to Frank da Cruz:
Columbia University Academic Information Systems
612 West 115th Street, New York, NY 10025 USA
Internet: fdc@columbia.edu
BITNET/EARN: FDCCU@CUVMA
C-Kermit 5A is documented in the book "Using C-Kermit" by Frank da Cruz and
Christine M. Gianone, Digital Press, Burlington, MA, USA, 1993. Digital Press
ISBN: 1-55558-108-0; Prentice-Hall ISBN: 0-13-037490-3. Price: US $34.95. In
USA, call DECdirect at 1-800-344-4825, refer to order number EY-J896E-DP.
NOTE: Several changes have been made to C-Kermit since the 5A(188) release.
These are listed in CKCKER.UPD.
THE C-KERMIT COMMAND PARSER
. There is no command recall or retry.
. VAX/VMS-style command parsing (arrow keys, etc) is not supported.
. EMACS- or VI-style command line editing is not supported.
. Typeahead is presently not allowed.
. Editing keys are hardwired (Ctrl-U, Ctrl-W, etc).
If you specify an alternate initialization file on the command line (using the
-y option) and the file doesn't exist or can't be opened, no error is reported.
If you use the backslash (\) prefix to enter a control character, space, or
question mark into a command literally, the backslash disappears and is
replaced by the quoted character. If it was a control character, it is shown
as a circumflex (^). This allows editing (backspace, delete, Ctrl-W) to work
correctly.
If you quote special characters in a filename (e.g. in the SEND command),
filename completion may seem to work incorrectly. For example, if you have a
file whose name is a*b (the name really contains an asterisk), and you type
"send a\\*<ESC>", the "b" will not appear, nor will Ctrl-R redisplay the
completed name correctly. But internally the file name is recognized anyway.
Question-mark help does not work during execution of an ASKQ command. The
question marks are simply accepted as text.
The maximum length for a variable name is 20 characters. For array
declarations and references, that includes the subscript. So, for example:
\%a[\m(max_services)]
is one character too long (this can be changed by redefining the symbol VNAML
in ckuusr.h and recompiling C-Kermit).
Some other maximums to watch out for: Symbol Value Defined in
Nesting level for command files: MAXTAKE 30 ckuusr.h
Nesting level for macros: MACLEVEL 50 ckuusr.h
Nesting level for FOR / WHILE loops: FORDEPTH 10 ckuusr.h
Number of macros: MAC_MAX 256 ckuusr.h
Size of INPUT buffer: INPBUFSIZ 256 ckuusr.h
Filespecs in MSEND command: MSENDMAX 100 ckuusr.h
Length of MSEND or GET string: FSPECL 300 ckuusr.h
Length for GOTO target label: LBLSIZ 50 ckuusr.h
Number of characters in a command: CMDBL 1024 ckucmd.h
Number of chars in a field of a command: ATMBL 256 ckucmd.h
\fexecute() recursion depth limit CMDDEP 20 ckucmd.h
ASK and ASKQ treat semicolon preceded by whitespace as a comment introducer.
If the user's response includes a semicolon preceded by whitespace, these and
all subsequent characters are discarded. To include a semicolon preceded by
whitespace, the user can prefix the semicolon with a backslash.
ASK and ASKQ strip leading and trailing spaces from what the user types. This
happens way down deep in the command parser -- it's nothing special about ASK
and friends. The only way around this that works in both C-Kermit and MS-DOS
Kermit is for the user (the one who is responding to the ASK prompt) to type
(the first) leading space as "\32" and the (final) trailing space as "\32".
In this example, the password begins with 2 leading blanks and ends with two
trailing blanks, and "Passwd:" is the ASK prompt:
Passwd:\32 secret \32
Of course, the user could also type *all* blanks as \32.
In OUTPUT commands only, \B and \\B send a BREAK signal, and \L and \\L send a
Long BREAK signal. If you really want to output a backslash followed by a B
or an L, use "output \\\\B" or "output \\\\L" (yes, four backslashes).
On certain SCO UNIX systems, the RETURN command doesn't work right. Example:
C-Kermit>define first return 1
C-Kermit>first
C-Kermit>echo \v(return)
return <--- This should say "1"
C-Kermit>
Cause and cure are unknown.
The "more?" prompting used during SHOW VARIABLES won't work right if the
INPUT buffer (\v(input)) contains linefeeds, in which case one or more lines
can scroll off the screen before you have a chance to read them.
MULTIPLE SESSIONS
C-Kermit does not support multiple sessions. When you SET LINE (or SET PORT,
same thing) to a new device, or SET HOST to a new host, the previous SET LINE
device or network host connection is closed, resulting in hangup of the modem
or termination of the network connection. In windowing environments like
NeXTSTEP, OS/2, etc, you can run separate copies of Kermit in different
windows to achieve multiple sessions.
NETWORK COMMUNICATION
On a TCP/IP TELNET connection, you should normally have PARITY set to NONE
and FLOW-CONTROL also set to NONE. If file transfer does not work with these
settings (for example, because the remote TELNET server only gives a 7-bit
data path), use SET PARITY SPACE. Do not use SET PARITY MARK, EVEN, or ODD
on a TELNET connection.
If echoing does not work right after connecting to a network host or after
dialing through a TCP/IP modem server, it probably means that the TELNET
server on the far end of the connection is executing the TELNET protocol
incorrectly. After initially connecting and discovering incorrect echoing
(characters are echoed twice, or not at all), escape back, give the
appropriate SET DUPLEX command (FULL or HALF), and then CONNECT again.
For a consistently misbehaving connection, you can automate this process in
a macro or TAKE file.
TELNET sessions are treated just like serial communications sessions as far
as "terminal bytesize" and "command bytesize" are concerned. If you need to
view 8-bit characters during a TELNET session, you must tell C-Kermit to
SET TERMINAL BYTESIZE 8, SET COMMAND BYTESIZE 8, and SET PARITY NONE.
MODEM DIALING
Here are a few points to clarify the purpose of SET DIAL SPEED-MATCHING:
1. This command does not do anything at all to the modem. Rather, it
tells C-Kermit whether or not to change its interface speed in response
to the speed given in the modem's CONNECT message. By default,
SPEED-MATCHING is ON, so Kermit does indeed attempt to change its speed.
2. This implies that when DIAL SPEED-MATCHING is ON:
(a) Your modem must be configured to report its *interface* speed in the
CONNECT message, rather than the connection (modulation) speed.
(b) Your computer (and C-Kermit) must support all connection speeds that
might be reported by your modem. SET SPEED ? will give you a list of
the speeds that your version of C-Kermit knows about.
3. If conditions (a) and (b) cannot be satisfied, then you must:
(a) Configure your modem to lock its interface speed
(b) Tell C-Kermit to SET DIAL SPEED-MATCHING OFF
To illustrate, suppose you have a V.32bis modem. When it connects to a
remote V.32bis modem, it might issue a message like:
CONNECT 14400
But 14400 bps is not a speed that is supported by most operating systems
and so C-Kermit might fail to adjust its speed according to this report.
Therefore, you must lock the modem's interface speed at a higher speed (such
as 19200, 38400, or 57600) that is supported by C-Kermit, set C-Kermit to the
same speed, and tell C-Kermit to SET DIAL SPEED-MATCHING OFF.
C-Kermit knows about a large number of modems, depending on how it was built
(type "set modem ?" and "show features" for further info). This knowledge is
imbedded in the SET MODEM and DIAL commands. If you are having trouble
dialing your modem, SET DIAL DISPLAY ON to watch the dialing interactions
between C-Kermit and your modem. Consult pages 65-66 of "Using C-Kermit" for
modem-dialing troubleshooting instructions.
If it takes your call longer to be completed than the timeout interval that
C-Kermit calculates, you can use the SET DIAL TIMEOUT command to override
C-Kermit's value. But beware: the modem has its own timeout for completing
the call. If it is a Hayes-like modem, C-Kermit adjusts the modem's value
too by setting register S7. But the maximum value for S7 might be smaller
than the time you need! In that case, C-Kermit sets S7 to 0, 255, or other
(modem-specific) value to signify "no timeout".
WARNING: Certain modems might have a maximum dial timeout shorter than what
Kermit expects it to be. If Kermit attempts to set register S7 to a value
higher than your modem's maximum, the modem will say "ERROR" and you will get
a "Failure to initialize modem" error. In that case, use SET DIAL TIMEOUT to
override C-Kermit's calculation of the timeout value with the highest value
that is legal for your modem, e.g. 60.
How to DIAL from a TCP/IP reverse terminal server (modem server):
1. (only if neccessary) SET TELNET ECHO REMOTE
2. SET HOST <terminal-server-ip-name-or-address> [ <port> ]
3. SET MODEM <modem-type>
4. (only if necessary) SET DIAL HANGUP OFF
5. DIAL <phone-number>
The order is important.
The SET DIAL KERMIT-SPOOF command works only for Telebit and US Robotics modem
types; it is OFF by default. You may wish to experiment with large packets
(1K or greater) and various window sizes with spoofing disabled in the modem.
In most situations the transfer rates achieved under these conditions are
better than with protocol spoofing turned on. Also, attribute (A) packets are
not passed by current Telebit modems with spoofing enabled so if they are
desired spoofing must be turned off.
DEC modems... Reportedly, these don't work right when connected to a DEC
terminal server -- result codes are never reported (on the other hand, this
might be a modem configuration problem). Dialing "by hand", "blind" still
works. Also, reportedly "For people who do have DEC modems directly connected
to DEC computers the DF03, DF100-series, and DF200-series modem dialers should
work. The only thing that is not straightforward is that the DF124-CA,
DF124-CM modems must use the the DF200-series since they speak Digital Modem
Command Language (DMCL) and AT commands. The Digital Scholar Plus is a DF242
so it uses the DF200-series."
If C-Kermit's dialing methods are insufficient for your purposes, you can
write a C-Kermit script program to do the dialing. Or you can use (or write)
another program to accomplish the dialing, and then run C-Kermit "underneath"
your dialing program by giving it the open file descriptor:
kermit -l <n> -m unknown
where <n> is the numeric file desciptor. (This feature is available in the
UNIX and OS/2 versions of C-Kermit.) Or you can modify the ckudia.c module.
HAYES AND COMPATIBLE MODEMS
C-Kermit should work correctly with Hayes and other modems that use the AT
command set. These include Hayes 1200, Hayes 2400, and Hayes 9600 bps modems,
compatibles, as well as Telebit and HST modems. See the next section for
Telebit information. C-Kermit sends AT commands to the modem and then reads
the modem's response. The code is designed to work whether the modem is
configured to echo its commands (E1) or not (E0), and whether it replies with
numeric (V0) or word (V1) result codes. C-Kermit does not change the echoing
state or result code mode of the modem. However, C-Kermit issues the Q0
command to the modem to ensure that it *does* produce result codes. C-Kermit
assumes the modem's Command Line Terminator (S3) is 13 (carriage return). If
it isn't, C-Kermit's dialog with the modem probably won't work correctly.
TELEBIT MODEM DIALING SUPPORT
There are numerous Telebit modem models, with differing capabilities and
features. C-Kermit tries to support them all in a model-independent way.
To use a Telebit modem, any model, SET MODEM as follows:
TELEBIT
Dial and attempt to connect using the highest protocol appropriate to
the interface speed between the computer and the modem, and fall back
automatically to the highest protocol and speed supported by the answering
modem. For example, if your interface speed is 19200 bps and you have a
PEP-capable Telebit, it will start in PEP mode, fall back to one of the
2400-bps standards, then one of the 1200 bps standards, etc, depending on
its configuration (see your Telebit manual).
PEP-TELEBIT
Dial in PEP mode, and connect only if the remote modem answers in PEP mode.
Does not work with Telebit models that do not support PEP. See Table III.
V32-TELEBIT
Dial in V.32 mode (9600 bps), fall back from there. Works only with Telebit
models that support V.32; see Table III. NOTE: V.32 calls are supposed to
work no matter what your interface speed is, but it has been observed that
when calling certain non-Telebit V.32 modems, the connection is not made
successfully unless C-Kermit's interface speed to the Telebit is 9600.
V42-TELEBIT
Enable V.42 error correction, allowing fallback to MNP, and from there to
direct (no error correction). NOTE: Fallback to MNP from V.42 is allowed
even if DIAL MNP-ENABLE is OFF. Works only with Telebit models supporting
V.42 error control. See Table III.
SLOW-TELEBIT
Dial at 2400 bps (V.22bis), fall back from there.
Telebit modems come in many models that differ not only as to features but
also which commands control which features. The features, commands, and
acceptable S-register values (and their meanings) can vary not only among
models, but even among different ROM versions on the same model. Rather than
have dozens of separate SET MODEM TELEBIT-xxx commands, C-Kermit queries the
modem for its model number with an ATI command, and then adjusts its modem
commands accordingly. Responses to the ATI command are shown in Table I.
---------------------------------------------------------------------------
Table I: Telebit Modem ATI Command Responses
---------------------------------------------------------------------------
ATI Model Numbers Examples
--- ------------- --------
123 Telebit in "total Hayes-1200" emulation mode
960 Telebit in Conventional Command (Hayes) mode
961 RA12C IBM PC internal original Trailblazer
962 RA12E External original Trailblazer, DCA Fastlink,
or Racal-Milgo RM1822
963 RM12C Rackmount original Trailblazer
964 T18PC IBM PC internal Trailblazer-Plus (TB+)
965 T18SA, T2SAA, T2SAS External TB+, T1600, T2000, T3000, WB, and later
or Ven-Tel Pathfinder EC18K (see below)
966 T18RMM Rackmount TB+
967 T2MC IBM PS/2 internal TB+
968 T1000 External T1000
969 ? QBlazer
971 T25SA External T2500 or T1500 (see below)
972 T25RM Rackmount T2500
---------------------------------------------------------------------------
Certain incompatible models show the same response to ATI. The ATI3
command is used to differentiate among them, as shown in Table II.
---------------------------------------------------------------------------
Table II: Telebit Modem ATI3 Command Responses
---------------------------------------------------------------------------
ATI If ATI3 Response
Response Contains Telebit Model Is
-------- ----------------- ----------------
965 "T1600" T1600
965 "T3000" T3000
965 "World" WorldBlazer
965 "Version B" TrailBlazer-Plus or T2000 external version 1
965 "TBSA" TrailBlazer-Plus or T2000 external version 2
965 "TBRM" TrailBlazer-Plus or T2000 rackmount version 2
965 "DC" Ven-Tel Pathfinder EC18K (= TB+ version 1)
971 "T1500" T1500
971 (anything else) T2500
----------------------------------------------------------------------------
The features of the various models and the commands used by Kermit to control
them are shown in Table III. The commands in the PEP column are used to force
PEP and allow compression (SET MODEM PEP-TELEBIT). The commands in the V.32
column are used with SET MODEM V32-TELEBIT. The commands in the V.42 column
are used with SET MODEM V42-TELEBIT. The commands in the MNP column are used
if SET DIAL MNP-ENABLE is ON and the modem type is TELEBIT, PEP-TELEBIT, or
V32-TELEBIT, SLOW-TELEBIT, but not V42-TELEBIT; if SET MNP-ENABLE is OFF, the
S-registers in the MNP column are set to 0. The Pass BREAK column shows the
commands used to ensure that the modem passes the BREAK signal through (rather
than treating it as an "escape-to-command-mode" signal).
-------------------------------------------------------------------------------
Table III. Telebit Modem Features and Commands
------+---------------------+-------+--------+--------+-------------+----------
| | | | | | Kermit
Model | PEP | V.32 | V.42 | MNP | Pass BREAK | Spoof
------+---------------------+-------+--------+--------+-------------+----------
TB | S50=255 S110=1 | No | No | S95=2 | S54=3 | PEP only
TB+ | S50=255 S110=1 | No | ** | S95=2 | S54=3 | PEP only
T2000 | S50=255 S110=1 | No | ** | S95=2 | S54=3 | PEP only
T1000 | S50=255 S110=1 | No | No | S95=2 | S54=3 | PEP only
T2500 | S50=255 S110=1 | S50=6 | No | S95=2 | S54=3 | PEP only
T1500 | No | S50=6 | ** | S95=2 | S54=3 | PEP,V.32
------+---------------------+-------+--------+--------+-------------+----------
T1600 | No | S50=6 | S180=2 | S180=3 | S61=0 S63=0 | PEP,V.32
T3000 | No | S50=6 | S180=2 | S180=3 | S61=0 S63=0 | PEP,V.32
QB | No | S50=6 | S180=2 | S180=3 | S61=0 S63=0 | No
WB | S50=255S190=1S191=7 | S50=6 | S180=2 | S180=3 | S61=0 S63=0 | PEP,V.32
------+---------------------+-------+--------+--------+-------------+----------
** For V.42 error control: "S50=0 S95=2 S97=1 S98=3 S106=1".
All models but the QBlazer support Kermit spoof (but see below).
Group I (old command set):
TB = Original TrailBlazer (PEP, MNP, V.22bis, V.22, Bell 212A & 103)
TB+ = TrailBlazer-Plus = TrailBlazer + V.42 (but only in new ROMs)
T1000 = TrailBlazer-Plus, speed <= 9600, no PEP compression
T2000 = TrailBlazer-Plus + SDLC (not used by Kermit, so same as TB+)
T2500 = TrailBlazer-Plus + V.32 (9600 bps)
T1500 = T2500 minus PEP
Group II (new command set):
T1600 = V.32, MNP, V.22bis, V.22, V.23, Bell 212A & 103
QB = QBlazer = T1600 without Kermit spoof and minus some other options
T3000 = T1600 + V.32bis (14400 bps)
WorldBlazer = T3000 + PEP + LZ and V.42bis compression + 76800 & 115200 bps.
C-Kermit does not attempt to control whether the modem changes its interface
speed to match the connection speed -- that is up to you; you can configure
the modem any way you prefer (using S51 or, to some extent on new-style modems
S180 and S181), but make sure that the modem's configuration agrees with
C-Kermit's DIAL SPEED-MATCHING setting. When DIAL SPEED-MATCHING is ON (the
default), C-Kermit changes its interface speed automatically according to the
speed reported in the modem's CONNECT message; when it is OFF, C-Kermit does
not change speed.
The DIAL KERMIT-SPOOF command is only effective for the Telebit models that
supply a Kermit spoof, that is, all but the QBlazer. If the Telebit model is
TrailBlazer, TrailBlazer-Plus, T1000, T2000, or T2500, PEP mode is forced even
if your SET MODEM command specified a Telebit modem type other than
PEP-TELEBIT, because the Kermit spoof only works in PEP mode on those models.
On the other models supporting the Kermit spoof, it works on both PEP
connections and V.32 MNP (but not V.42) connections. Thus, you might also
have to SET MODEM MNP-ENABLE ON in order to get the Kermit Spoof to work on
these newer models when making a V.32 connection.
SHOW DIAL does not show the complete initialization string for Telebit modems.
Telebit modems are initialized in several steps, and the initialization
command depends upon your current communication parameters, which model of
Telebit modem you have (which C-Kermit learns during the modem initialization
process), and other factors. If you use the SET DIAL INIT-STRING command to
change the initialization string, this disables the multistep process and uses
only the string that you have specified.
If you want to use the built-in multi-step process, but you also want to
override one or more of the settings that are done in this process, or add
additional settings, you can use SET DIAL DIAL-COMMAND to add commands to the
dial string (which is normally ATD%s\13), for example "SET DIAL DIAL-COMMAND
AT&C1&D2S181=1DT%s\13".
DIALING AND FLOW CONTROL
If you have SET FLOW to any of the hardware options supported by your version
of C-Kermit, such as RTS/CTS, and if C-Kermit knows how to set the flow
control on your modem, it will do this as part of the DIAL command. Caution:
. If C-Kermit's FLOW-CONTROL setting is Xon/Xoff or other type of software
flow control, C-Kermit will not attempt to change your modem's flow control
setting, since software flow control is most commonly used end-to-end. One
way to engage Xon/Xoff flow control directly between C-Kermit and the
local modem is to change your modem's DIAL INIT-STRING to do it.
. If your version of C-Kermit does not support SET FLOW RTS/CTS (or other
hardware options), then C-Kermit will not attempt to change your modem's
flow control setting. Change your modem's DIAL INIT-STRING to do it.
Hardware flow control options are presently handled only for Telebit modems.
On other modem types, you can set the flow control outside of Kermit, or
change Kermit's DIAL INIT-STRING.
Most modern modems support RTS/CTS (if they support any hardware flow control
at all), but some computers use different RS-232 circuits for the same
purposes, e.g. DTR and CD, or DTR and CTS. In such cases, you might be able
to make your computer work with your modem by appropriately cross-wiring the
circuits in the cable connector, for example the computer's DTR to the modem's
RTS, and modem's CD to the computer's CTS. HOWEVER, C-Kermit does not know
you have done this. So if you have (say) SET FLOW DTR/CD, C-Kermit will make
no attempt to tell the modem to use RTS/CTS. You probably did this yourself
when you configured the modem; if not, you can put the appropriate command in
the DIAL INIT-STRING or DIAL-COMMAND.
C-Kermit is fully compatible with "TIES" (Time Independent Escape Sequence)
modems. A TIES modem does not require any guard time around its escape
sequence. The following text:
+++ATH0
if sent through a TIES modem, for example because you were uploading this
file through it, could pop the modem back into command mode and make it hang
up the connection. Newer versions of the Telebit T1600 and T3000 (version
LA3.01E firmware and later), and all WorldBlazers, use TIES.
However, unlike other protocols (such as XMODEM, YMODEM, ZMODEM, SLIP, PPP),
Kermit handles this situation very nicely. Any sequence of 3 or more repeated
characters is encoded in a special way, so no matter what your escape sequence
is, Kermit transfers won't contain it (note: these comments apply to transfers
between any pair of Kermit programs that negotiate repeat-count compression;
such programs include C-Kermit, MS-DOS Kermit, IBM Mainframe Kermit, and
PDP-11 Kermit). For example, if your escape sequence is +++, and +++ appears
in your data, it is encoded for transmission as ~#+.
TIES can still bite you, however, if you are using Kermit's TRANSMIT command
to upload files through a TIES modem, or, indeed, any time your terminal or
computer sends the escape sequence into the originating modem. If you are
using a Telebit TIES modem, you can turn off the modem's escape sequence
recognition with:
AT S48=0 S2=255
But when escape sequence recognition is turned off, "modem hangup"
(<pause>+++<pause>ATH0<CR>) will not work, so you should also be sure to SET
DIAL MODEM-HANGUP OFF.
TERMINAL EMULATION
Except for the OS/2 and Macintosh versions, C-Kermit does not emulate any kind
of terminal. Rather, it acts more or less as a "transparent pipe", passing
the characters you type during a CONNECT session to the remote host, and
sending the characters received from the remote host to your screen. Whatever
is controlling your keyboard and screen provides the specific terminal
emulation: a real terminal, a PC running a terminal emulator, etc, or (in the
case of a self-contained workstation) your console driver, a terminal window,
xterm, etc.
There are several exceptions to the "transparent pipe" rule:
- During a TELNET ("set host") session, C-Kermit itself executes the
TELNET protocol and performs TELNET negotiations. (But it does not
perform TN3270 protocol or any other type of 3270 terminal emulation.)
- If you have changed your keyboard mapping using SET KEY, C-Kermit replaces
the characters you type with the characters or strings they are mapped to.
- If you SET your TERMINAL CHARACTER-SET to anything but TRANSPARENT,
C-Kermit translates your keystrokes (after applying any SET KEY
definitions) before transmitting them, and translates received characters
before showing them on your screen.
- If your remote and/or local TERMINAL CHARACTER-SET is an ISO 646 7-bit
national character set, such as German, French, Italian, Swedish, etc, or
Short KOI used for Cyrillic, C-Kermit's CONNECT command automatically skips
over ANSI escape sequences to avoid translating their characters. Only
ANSI/ISO standard (VT100/200/300-like) 7-bit escape sequence formats are
supported for this purpose, no proprietary schemes like H-P, Televideo,
Tektronix, etc.
If you are running C-Kermit under a console driver, or in a terminal window,
that emulates the VT100, and use C-Kermit to log in to a VMS system, the
console driver or terminal window (not Kermit) is supposed to reply to the
"what are you?" query (ESC Z) from the VAX. If it doesn't, and you can't make
it do so, then you can (a) live with the "unknown terminal" problem; (b) tell
VMS to SET TERMINAL/DEVICE=VT100; (c) program a key using SET KEY to send the
appropriate sequence and then punch the key at the right time; or (d) use the
VMSLOGIN macro that is defined in CKERMIT.INI to do this for you
automatically.
SET SESSION-LOG { TEXT, BINARY }, which is effective in UNIX and AOS/VS but
not other C-Kermit versions, removes CR, DEL, NUL, XON, and XOFF characters
("Using C-Kermit" neglects to mention that XON and XOFF are removed). The
TEXT-mode setting is ineffective during SCRIPT command execution, as well as
on X.25 connections.
KEY MAPPING
Except in the OS/2 and Macintosh versions, C-Kermit's key mapping facilities
are limited to normal "ASCII" keys, and cannot be used with function keys,
arrow keys, arcane key combinations, etc. Since C-Kermit runs on such a wide
variety of hardware platforms (including, for example, more than 280 different
UNIX platforms), it is not possible for C-Kermit to support every conceivable
keyboard under every release of every UNIX (or VMS, or ...) product on every
different kind of computer possibly under all manner of different console
drivers.
In technical terms, C-Kermit uses the read() function to read keystrokes, and
read() returns a single byte (value 0 through 255). C-Kermit's SET KEY
function applies to these single-byte codes. "Extended function" keys, such
as F-keys, arrow keys, etc, usually return either a 2-byte "scan code" or else
a character string (such as an escape sequence like "ESC O p"). In both
cases, C-Kermit has no way to tell the difference between such multibyte key
values, and the corresponding series of single-byte key values. This could
only be done by accessing the keyboard at a much lower level in a highly
system-dependent manner, probably requiring tens of thousands of lines of code
to support even a sampling of the most popular workstation / OS combinations.
However, most workstation console drivers (terminal emulation windows, etc)
include their own key-mapping facility. For example, on an IBM RS/6000, the
AIXterm program (in whose window you would run C-Kermit) allows rebinding of
the F1-F12 keys to arbitrary strings. The same might or might not be true of
DECterm windows, Sun "vttool" or "crttool" windows, etc. Consult the
technical documentation for your workstation or emulator.
The SET KEY command (except in OS/2) does not allow a key definition to be
(or contain) the NUL (\0) character.
THE TRANSMIT COMMAND
Session logging is inactive during the TRANSMIT command, even if you have
given a LOG SESSION command.
FILE TRANSFER
When referring to MS-DOS, Atari ST, OS/2, or other file specifications that
contain backslash characters in a C-Kermit command, you must double each
backslash, for example:
C-Kermit>get c:\\directory\\foo.txt
This is because backslash is used in C-Kermit commands for introducing special
character codes, variables, functions, etc. If you are sending this GET
command to another copy of C-Kermit running as a server, for example on OS/2
or the Atari ST, it too treats backslashes as prefix characters, so you will
need 4 (yes, 4) copies of each backslash:
C-Kermit>get c:\\\\directory\\\\foo.txt
Attempting to cancel local-mode file reception at a very early stage (i.e.
before data packets are exchanged) with X or Z does not work. Workarounds:
Use E or Ctrl-C instead, or wait until the first data packets are sent.
If C-Kermit is sending a file, remote-mode packet-mode breakout (Ctrl-C Ctrl-C
by default) is not effective until after C-Kermit sends its first packet. If
C-Kermit is receiving a file or is in server mode, it will be effective right
away. In the former case, the SET DELAY value determines the earliest time at
which you can break out of packet mode.
Some communication programs have errors in their implementation of Kermit
attribute packets. If you get an error message from your communication
program like "Attribute error", tell C-Kermit to SET ATTRIBUTES OFF. Better
yet, switch to a real Kermit program, such as MS-DOS Kermit.
Occasionally, when in receiving files in remote mode using a large window
size, attempts to cancel a file (X) can take a long time.
The fullscreen file transfer display will not work right if your terminal type
is set incorrectly, or is not known to the host operating system. Even when
it does work, it might slow down your file transfers a bit, especially on
high-speed network connections. On certain small computers, it has been
reported to cause increased disk activity due to swapping or paging. The
fullscreen display is not particularly useful with speaking or Braille devices.
If you have trouble transferring files over a TCP/IP connection, give the
command:
SET PARITY SPACE
and try again. If that doesn't work, also try a shorter packet length.
On the other hand, if file transfers through a TCP/IP connection work, but
are very slow, use a longer packet length, 2000 or more. Make sure FLOW is
NONE.
Some communication software claims to implement sliding windows, but does so
incorrectly. If sliding window transfers fail, set C-Kermit's window size to
the smallest one that works, for example:
SET WINDOW 1
The UNIX version of C-Kermit discards carriage returns when receiving files
in text mode. Thus, "bare" carriage returns (sometimes used to achieve
overstriking) are lost.
SET FILE COLLISION BACKUP is the default. This means:
- If you send the same file lots of times, there will be many backup files.
There is no automatic mechanism within Kermit to delete them, no notion of
a "version retention count", etc.
- If a file arrives that has the same name as a directory, the file transfer
fails. Send the file with another name, or use SET FILE COLLISION RENAME.
SET FILE COLLISION UPDATE depends on the date/time stamp in the attribute
packet. However, this is recorded in local time, not GMT, and there is no
indication of time zone. The time is expressed to the precision of 1 second,
but some file systems do not record with this precision -- for example, MS-DOS
records the file date/time only to the nearest 2 seconds. This might cause
update operations to send more files than necessary.
SET FILE COLLISION OVERWRITE is risky, use it with caution. Under certain
conditions, the existing file can be deleted even if the incoming file is
refused.
When C-Kermit is receiving files from another Kermit program that has been
given the MAIL or REMOTE PRINT command, C-Kermit follows the current filename
collision action. This can be disconcerting if the action was (for example)
BACKUP, because the existing file will be renamed, and the new file will be
mailed (or printed) and then deleted. Kermit cannot temporarily change to
RENAME because the file collision action occurs when the filename packet is
received, and the PRINT or MAIL disposition only comes later, in the Attribute
packet.
The STATISTICS command will produce an incorrect efficiency report if (a) it
does not know the true communication speed (e.g. on a network connection), or
(b) it knows the true serial interface speed to a modem, but the modem is
using a different communication speed with the other modem. Similarly, in
these circumstances, C-Kermit's automatic calculation of the packet timeout
interval might also be incorrect, which can cause file transfers to fail. One
solution to the latter problem is to SET SEND and RECEIVE TIMEOUT to
appropriate values for your true communication speed and packet length.
TELNET option negotiations are not handled during file transfer.
Why is Kermit file transfer over a TCP/IP connection slower than FTP? Because
the Kermit program on the remote end of the connection is not running directly
on a TCP socket, but rather running underneath a TELNET server, usually on a
pseudoterminal and under a login shell, with the vast amounts of per-character
overhead all of that implies. Future Kermit releases will be able to act
directly as TCP servers, eliminating all this overhead.
BUG: C-Kermit (at least the UNIX version), when told to send a file to which
the user has directory-listing access but does not have read access, goes into
protocol mode, telling the user to escape back and give a RECEIVE command,
etc, and only then does it notice that the file can't be opened, and gives a
"?Read access denied" message -- but this is a terminal message, not an
Error packet, so the user (having escaped back already) never sees it.
SCRIPT PROGRAMMING
The CKERMIT.INI file that was originally distributed with C-Kermit 5A(188)
and (189) contained a nonfunctional CISLOGIN (CompuServe Login) macro.
Fixed in CKERMIT.INI dated September 2, 1993, or later.
You can't use END or RETURN statements in FOR, WHILE, and XIF commands (you
can use them, but they won't do what you expect).
INPUT and REINPUT caseless string comparisons do not work for non-ASCII
(international) characters. Workaround: SET INPUT CASE OBSERVE. Even then,
the "lexically less than" and "lexically greater than" operations (IF LLT, IF
LGT) probably won't work as expected. The same is true for the
case-conversion functions \Flower() and \Fupper(). C-Kermit does not know the
collating sequence for different character sets and languages.
You can't include a NUL character (\0) in C-Kermit command text without
terminating the character string in which it appears. For example:
echo In these brackets [\0] is a NUL
will echo "In these brackets [". This applies to ECHO, INPUT, OUTPUT, and all
other commands. This is because C-language strings are terminated internally
by the NUL character, and it allows all of C-Kermit's string comparison and
manipulation functions to work in the normal way.
To illustrate:
INPUT 5 \0
is equivalent to:
INPUT 5
and:
INPUT 5 ABC\0DEF
is equivalent to:
INPUT 5 ABC
INPUT operations discard and ignore NUL characters that arrive from the
communication device, meaning that they do not figure into matching operations
(e.g. A<NUL>B matches AB); they are not deposited in the INPUT buffer
(\v(input)); and they are not counted in \v(incount), with two exceptions:
1. An arriving NUL character restarts the INPUT SILENCE timer.
2. An arriving NUL character terminates the INPUT command with the
SUCCESS condition if the INPUT command was given an empty search
string. In this case \v(incount) is set to 1.
Also, the \v(inchar) variable is null (completely empty) if the last INPUT
character was NUL. That is, there is no way to tell only by looking at
\v(inchar) the difference between a NUL that was INPUT and no INPUT at all.
If the INPUT command succeeded but \v(inchar) is empty, then a NUL character
was input. Also, \v(incount) will be set to 1.
\v(incount) and \v(inchar) are NOT affected by the CLEAR command.
GOTO can be used sort of like switch/case. For example, if you know that the
value of \%a is 1, 2, or 3, you can "goto \%a" provided you have labels :1,
:2, and :3. What it missing, however, is an automatic way to trap failing
GOTOs, similar to the "default:" clause of a C switch() statement.
The following script program:
asg \%n \ffiles(\%1)
set count \%n
:loop
asg \%f \fnextfile()
send \%f
rem host print \%f
if count goto loop
does not work as expected. The SEND command (and any other command that
parses a filename) implicitly calls the same internal function that \ffiles()
calls, and thus destroys the file list set up in the first line. To
accomplish this type of operation: (1) give the wild filespec to \ffiles();
(2) loop through the file list and assign each filename to an array element;
(3) use the array of filenames in subsequent file-related commands. Example:
asg \%n \ffiles(\%1)
declare \&f[\%n]
for \%i 1 \%n 1 { asg \&f[\%i] \fnextfile() }
for \%i 1 \%n 1 { -
send \&f[\%i], -
rem host print \&f[\%i] -
}
Certain settings are local to each command level, meaning that subordinate
command levels (macros or command files) can change them without affecting
their values at higher command levels. When a new command level is invoked,
the value is inherited from the previous level. These settings are:
CASE
COUNT and \v(count)
INPUT CASE
INPUT TIMEOUT
MACRO ERROR
TAKE ERROR
This arrangement allows CASE, TIMEOUT, and ERROR settings, which are used to
control automatic exit from a command file or macro upon error, to be
automatically restored when the command file or macro exits.
The COUNT variable follows this rule too, which permits nested SET COUNT /
IF COUNT loops, as in this example in which the inner loop counts down from
the current COUNT value of the outer loop (try it):
DEFINE INNER WHILE COUNT { WRITE SCREEN { Inner:}, SHOW COUNT }
SET COUNT 5
WHILE COUNT { WRITE SCREEN Outer:, SHOW COUNT, DO INNER }
Keep in mind that an inferior command level cannot manipulate the COUNT
value held by a higher level. For example:
DEFINE OOFA SHOW COUNT, IF COUNT GOTO LOOP
SET COUNT 5
:LOOP
OOFA
ECHO Done
results in an infinite loop; the COUNT value remains at 5 because it is never
decremented at the same level at which it was set.
NOTE: "WHILE COUNT" did not work prior to edit 095 of ckuusr.c, 19 Jan 93.
(End of CKCKER.BWR)