C-Kermit 8.0 VMS Hints and Tips

   As of C-Kermit version: 8.0.209, 17 March 2003
   This file last updated: Sun Mar 9 18:51:13 2003 (New York City time)

IF YOU ARE READING A PLAIN-TEXT version of this document, note that this file is a plain-text dump of a Web page. You can visit the original (and possibly more up-to-date) Web page here:

  http://www.columbia.edu/kermit/ckvbwr.html

Authors:

F. da Cruz, C. Gianone, Columbia University, New York, NY.
Terry Kennedy, Saint Peters College, Jersey City, NJ.

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CONTENTS

  1. INTRODUCTION
  2. THE C-KERMIT COMMAND PARSER
  3. COMMUNICATIONS
  4. GENERAL FAILURES
  5. LOCAL FILE OPERATIONS
  6. FILE TRANSFER
  7. OTHER TOPICS

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1. INTRODUCTION

SECTION CONTENTS:

  1.1. Terminology
  1.2. Documentation
  1.3. Technical Support
  1.4. Other Sources of Information

This is what used to be called the "beware file" for VMS C-Kermit, formerly known as CKVBWR.TXT (and before that CKVKER.BWR). This edition is current as of C-Kermit 8.0. It contains hints and tips specific to the VMS version of C-Kermit not necessarily found in the manual, or which developed since the manual was published (Section 1.1). The General C-Kermit Hints and Tips document:

  http://www.columbia.edu/kermit/ckcbwr.html

formerly known as CKCBWR.TXT (and before that CKCKER.BWR), contains similar material that applies to all C-Kermit versions: Unix, VMS, VOS, etc.

VMS C-Kermit installation instructions are in a separate document:

  http://www.columbia.edu/kermit/ckvins.html

(formerly known as CKVINS.TXT. Please be sure you have read that file before concluding that C-Kermit isn't working right on VMS.

[ C-Kermit ] [ Kermit Home ]

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1.1. Terminology

"VMS" as used in this document refers to both VMS and OpenVMS on VAX processors and OpenVMS on Alpha (formerly known as AXP) processors, and presumably any other architectures that VMS will be adapted to, such as IA64, PowerPC, or PA-RISC. Most of the words in the first part of the previous sentence are or were trademarks (TM) of Digital Equipment Corporation and/or Compaq Computer Corporation.

"DEC" is the way most people refer to Digital Equipment Corporation.

Digital Equipment Corporation was acquired in 1998 by Compaq Computer Corporation, and thus references to Digital Equipment Corporation or DEC should be interpreted accordingly in light of the evolving integration, transfer of copyrights and licenses, product renaming, etc. In this document we stick with the traditional and familiar nomenclature. Compaq, in turn, is on its way into the stomach of an even bigger fish, most likely Hewlett Packard.

There might be contradictory bits of advice in this file, since much of the information was culled from different sources at different times. Comments, reports, suggestions, contributions are always welcome.

[ C-Kermit ] [ Kermit Home ]

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1.2. Documentation

1. Frank da Cruz and Christine M. Gianone, Using C-Kermit, Second Edition, Digital Press / Butterworth-Heinemann, Woburn, MA, 1997, 622 pages, ISBN 1-55558-164-1. This is a printed book. It covers C-Kermit 6.0.

2. The C-Kermit 7.0 Supplement: http://www.columbia.edu/kermit/ckermit70.html

3. The C-Kermit 8.0 Supplement: http://www.columbia.edu/kermit/ckermit80.html

The C-Kermit home page is here:

  http://www.columbia.edu/kermit/ckermit.html

[ C-Kermit ] [ Kermit Home ]

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1.3. Technical Support

Email:	kermit-support@columbia.edu
News:	comp.protocols.kermit.announce comp.protocols.kermit.misc	<-- Announcements, moderated <-- Discussion, unmoderated
Web:	http://www.columbia.edu/kermit/ http://www.kermit-project.org/ http://www.columbia.edu/kermit/faq.html	<-- Kermit Project Home Page <-- Alternative Web address <-- Frequently Asked Questions
Post:	The Kermit Project Columbia University 612 West 115th Street New York NY 10025-7799 USA
Fax:	+1 (212) 662-6442

[ C-Kermit ] [ Kermit Home ]

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1.4. Other Sources of Information

The OpenVMS Frequently Asked Questions (FAQ) document is available at various sites on the Internet, including (checked Feb 2003):

  http://www.openvms.compaq.com/wizard/openvms_faq.html
  ftp://rtfm.mit.edu/pub/usenet/news.answers/dec-faq/vms

The following newsgroup is dedicated to discussion of VMS-related topics:

  comp.os.vms

And this one to more general DEC-related topics:

  comp.sys.dec

[ C-Kermit ] [ Kermit Home ]

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2. THE C-KERMIT COMMAND PARSER

SECTION CONTENTS:

  2.1. Running C-Kermit in DCL Command Procedures
  2.2. Running C-Kermit from ALL-IN-1
  2.3. Running C-Kermit under DECIntact

When you start C-Kermit at your terminal, everything should work as expected. You get the prompt, you can type commands, your keystrokes echo (once, not zero or two times), ? gives help, Ctrl-C interrupts a command in execution and returns to the prompt. However, VMS offers a wide variety of "other" environments (Batch, Spawn'd, DCL command procedures, pipes, mailboxes, ...) in which programs can execute, and Kermit tries to recognize and adapt itself to them automatically, but this might not always work. Therefore, two command-line options are provided so you can force the required adaptations:

-z

Force foreground. If Kermit thinks it's in the background, i.e. that it does not have a connection to a command terminal (your keyboard), it is likely to (a) not issue a prompt; (b) not echo your keystrokes; (c) not respond to "?", Esc, etc. Use the -z option to force it to treat SYS$INPUT as a real terminal, even if it doesn't seem to be one.

"-B"

Force Background (the doublequotes are necessary to prevent DCL from lowercasing the B). This is for the opposite situation: If Kermit thinks SYS$INPUT is a real terminal, but it's not, then Kermit command procedures might fail immediately with "?Can't initialize" or somesuch. Use the "-B" option to tell Kermit it doesn't really have a terminal.

VMS-style command-line editing (arrow keys, etc) is not supported (you can, however, use up and down arrow keys for command recall in C-Kermit 8.0.201 and later). Kermit does not use the VMS F$PARSE facility -- it has its own command parser that lacks certain features of F$PARSE (arrow-key editing, etc) but has many other features that F$PARSE lacks: context-sensitive "?"-help and file lists, keyword and filename completion, filename menus, variables, macros, etc. C-Kermit does, however, support command recall via Ctrl-B (or Ctrl-P, same thing) and Ctrl-N.

If you write a DCL command file that starts Kermit with a command-file name as its first command-line argument, e.g.:

  $ kermit oofa.ksc

and then SUBMIT this DCL command file as a batch job, be aware that the batch job is executed out of your login directory, so if the command file (OOFA.KSC in this case) is not in your login directory, you must either SET DEFAULT to the directory it is in, or else give a fully qualified filename:

  $ set default [mydir.mysubdir]
  $ kermit oofa.ksc

or:

  $ kermit [mydir.mysubdir]oofa.ksc

Contrary to expectations of VMS users, the MSEND command does not use commas to separate file specifications. E.g. say this:

  C-Kermit>msend ckc*.% cku*.% ckv*.%

not this:

  C-Kermit>msend ckc*.%, cku*.%, ckv*.%

CD (Change Directory) to a DECnet node does not work in VMS C-Kermit.

The VMS 6.1 and 6.2 C Run Time Libraries (CRTL) have bugs in them that prevent the CD command from working totally right when given no argument, which is supposed to put you back in your login directory, when SYS$LOGIN indicates a search list and/or hidden directories. C-Kermit tries to work around this bug (technical explanation: use CRTL chdir(), which is supposed to do all the right things; if it fails then use the VMS sys$setddir() system service, which works in cases where VMS 6.1/6.2 CRTL doesn't, but which applies to your whole job rather than to Kermit's process tree only, and then when Kermit exits, it tries to use sys$setddir() again to restore your startup directory -- but if C-Kermit is interrupted or terminated abnormally this won't work, etc etc.) If you have trouble with all this, then CD to the desired device:directory explicitly or define a macro to do this. (The problem, if it occurs, is in the library that C-Kermit was linked with, not the one on your VMS system, so installing ECOs, etc, would not help.)

OPEN !WRITE does not work in VMS C-Kermit.

VMS C-Kermit does not provide program status codes in the normal VMS manner. Rather, it returns the codes described on pp. 323-324 of "Using C-Kermit", by assigning them to the symbol CKERMIT_STATUS. For example, if a RECEIVE operation failed:

  $ show symbol ckermit_status
    CKERMIT_STATUS == "4"
  $

Arguments supplied to the EXIT (or QUIT) commands take precedence:

  C-Kermit>exit 1234
  $ show symbol ckermit_status
    CKERMIT_STATUS == "1234"
  $

If C-Kermit encounters no execution errors, and EXIT (QUIT) is given without an operand, then:

  C-Kermit>exit
  $ show symbol ckermit_status
    CKERMIT_STATUS == "0"
  $

You can use the CKERMIT_STATUS symbol as in this DCL example:

  $ kermit -s oofa.txt
  $ if ckermit_status .eq. 0 then goto ok

[ C-Kermit ] [ Kermit Home ]

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2.1. Running C-Kermit in DCL Command Procedures

It is often desirable to wrap C-Kermit in a DCL command procedure. Such a procedure, for example OOFA.COM, can be run either directly on your job's controlling terminal by:

  $ @OOFA [ parameters ]

or as a batch job via:

  $ SUBMIT OOFA [ switches ]

When you are writing a DCL command procedure that runs C-Kermit, you must make a choice:

1. If you want to be able to include Kermit commands in the DCL procedure as "image data" (i.e. lines that don't start with $), then you can not include any Kermit commands that would require access to the real console terminal's keyboard and screen, such as CONNECT. That is, the person who runs the DCL procedure can not interact directly with a remote computer. This type of DCL command procedure can be run either on a terminal via @, or as a batch job via SUBMIT.

2. If you want the user to be able to interact directly with the remote computer through Kermit's CONNECT command, then:
   1. The DCL procedure can be run only with @, not with SUBMIT. That is, it cannot be a batch job; it must have access to the console terminal.

   2. You must include the following DCL command in the DCL procedure immediately before starting Kermit:

        $ DEFINE /USER SYS$INPUT SYS$COMMAND
      

   3. You can not include Kermit commands as "image data" in the DCL command procedure. Instead, you must create a separate Kermit command file, and use command-line arguments to instruct Kermit to execute it; for example:

        $ define /user/nolog sys$input sys$command
        $! Execute oofa.ksc instead of normal initialization file.
        $ kermit -y oofa.ksc
      

      or:

        $ define /user sys$input sys$command
        $! Execute oofa.ksc after executing normal initialization file.
        $ kermit "-C" "take oofa.ksc"
      

Here is a sample DCL command procedure of the first type, which can be run either on the controlling terminal or as a batch procedure, and requires no interaction from the user. Lines beginning with dollar sign ($) are DCL commands, other lines are fed to the application program (Kermit).

  1. $ write sys$output "Hello from DCL"
  2. $ set default [myuserid.mysubdirectory]
  3. $ kermit
  4. set background off
  5. echo Hello from C-Kermit
  6. @ write sys$output "Hello from DCL from inside C-Kermit"
  7. take oofa.ksc
  8. exit
  9. $ write sys$output "All done."

(The numbers are not part of the file.) Lines 1-3 are DCL commands. Line 3 starts C-Kermit. Lines 4-8 are C-Kermit commands.

Line 4 causes Kermit prompts and commands read as image data from the remainder of the .COM file to be echoed to the batch log. Normally this is not done, and the only material that goes into the batch log is output from Kermit commands like ECHO (next item). The SET BACKGROUND OFF command tells Kermit that even though it is running in batch, it should issue its prompt and echo its commands. You can accomplish the same thing by starting Kermit the "-z" command-line option (line 3 would be "$ kermit -z").

Line 5 shows how to enter messages in the batch log. Line 6 shows how to run DCL commands from within Kermit (you can use @ (at-sign), ! (exclamation mark), or the word RUN -- all of them are synonyms, followed by a DCL command). Line 8 exits from C-Kermit back to DCL.

In line 7, C-Kermit is told to execute a script program from another file, OOFA.KSC. Script programs to be run during the batch session are best kept in separate C-Kermit command files because certain commands, notably GOTO, FOR, WHILE, and IF, do not work when entered in the interactive command stream. Here is a sample command file:

  set take echo on      ; Make Kermit commands appear in the batch log
  set take error on     ; This stops execution automatically upon error
  set input echo on     ; This makes INPUT material appear in the batch log
  set host blah         ; Make a network connection to host "blah"
  set file brief serial ; Use SERIAL or NONE for the batch log, not FULL or CRT
  input 5 login:        ; Wait for a login prompt
  output myuserid\13    ; Send my user ID and a carriage return
  input 5 Password:     ; Wait for password prompt
  output \$(P1)\13      ; Send my password (see below) and a carriage return
  input 20 \13\10$\32   ; Wait for system prompt
  output kermit\13      ; Start Kermit on host "blah"
  input 5 Kermit>       ; Wait for Kermit> prompt
  output server\13      ; Put remote Kermit in server mode
  in 5 READY TO SERVE...; Wait for READY message
  get oofa.txt          ; Get a file from the remote server
  bye                   ; Terminate the remote session
  end                   ; Return to local C-Kermit prompt

Note that the commands from a TAKE file are not echoed to the batch log unless you include SET TAKE ECHO ON.

VERY IMPORTANT: Batched login scripts are inherently insecure because the passwords are visible in plaintext, either in a file or else in the batch queue entry. VMS presently offers no secure way that we know of to enter a password into a batch job.

Two very insecure methods can be used:

1. Put the password in the Kermit script file. The risk here is that anybody who gains access to the file, or to the system backup tapes, can learn your password on the remote system.

2. Give the password as a parameter to the SUBMIT command when starting the batch job, for example:

    $ SUBMIT OOFA /NOTIFY /PARAM=("mypassword")
   

   (This sets the DCL parameter P1 to your password on the remote host (for further information, give the DCL command "help submit /param"). Quotation marks are necessary to preserve lowercase letters (important when logging in to UNIX hosts). DCL parameters may be referenced in Kermit commands as \$(P1), \$(P2), etc.) The disadvantage here is that the VMS SHOW ENTRY/FULL command displays the parameters from your SUBMIT command, making the password visible to (at least) the system operator, and (most likely) also to other users, such as members of your group (batch queues are, by default, read-accessible by all members of their group).

Both methods can be made somewhat safer by adjusting the protections on the files and/or batch queues that will contain sensitive information, but there can be no guarantees. Therefore: EXERCISE EXTREME CAUTION with passwords in login scripts and batch jobs.

And please note further that passwords passed in plain text -- as they still must be in most cases, particularly those involving dialup access -- are subject to discovery by various other means, including, but not limited to, wire tapping, Ethernet packet tracing, etc.

[ C-Kermit ] [ Kermit Home ]

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2.2. Running C-Kermit from ALL-IN-1

Contibuted by: Dr. David Kelly, Australian Environmental Protection Authority, kellyd@airmoon.epa.nsw.gov.au

ALL-IN-1 uses mailboxes (MBX) devices, rather than terminals. TT: is reassigned from the user's controlling terminal to a mailbox device. C-Kermit uses TT: as its default line device and so doesn't work straight off under ALL-IN-1. SYS$INPUT is reassigned to something else again. SYS$OUTPUT remains assigned to the user's original terminal line so it can be used to specify the line device for C-Kermit when called from within ALL-IN-1. Below is a script which can be run from ALL-IN-1 which calls C-Kermit to receive a file. SYS$OUTPUT is temporarily redefined to stop some guff showing on the screen.

  $! RECEIVE_FROM_PC.COM
  $!
  $! Transfer file from PC into ALL-IN-1 using KERMIT
  $! Invoked by TRANSFER_PC_TO_A1.SCP, which is in turn called by the RF
  $! option on DT menu.
  $!
  $ set noon
  $ on control_y then goto exit
  $
  $       tt1=f$trnlnm("sys$output")
  $       kermit :== $epa__system:Ckermit
  $       define/user sys$input sys$command
  $       define sys$output sys$login:del.txt
  $       kermit -l 'tt1' -b 9600 -r -a a1file.a1f -q -i
  $       deassign sys$output
  $       del sys$login:del.txt;
  $exit:
  $ exit

Similarly a file can be sent :

  $! SEND_TO_PC.COM
  $! Transfer document from ALL-IN-1 to the PC
  $! invoked by TRANSFER_A1_TO_PC.SCP which is, in turn, called by the
  $! SF option on the DT menu
  $!
  $ set noon
  $ on control_y then goto exit
  $!
  $       write oamailbox "OA GET #CURDOC_FILENAM"
  $       @dclmailbox:
  $       a1file = "''result'"
  $       vmsfile = "A1FILE.A1F"
  $       copy/nolog/noconfirm 'a1file' 'vmsfile'
  $       kermit :== $epa__system:Ckermit
  $       define/user sys$input sys$command
  $       tt1=f$trnlnm("sys$output")
  $       define sys$output sys$login:del.txt
  $       kermit -l 'tt1' -b 9600 -s A1FILE.A1F -q -i
  $       deassign sys$output
  $       del sys$login:del.txt;
  $       if $severity .le. 1 then goto exit
  $! if an error occurs, tell ALL-IN-1
  $       write oamailbox "OA GET $PC_KERMIT_STATUS=0"
  $       @dclmailbox:
  $exit:
  $ deletex/nolog a1file.a1f;*
  $ exit

[ C-Kermit ] [ Kermit Home ]

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2.3. Running C-Kermit under DECintact

To use C-Kermit in remote mode under DECIntact, you must:

1. Have C-Kermit 7.0 or later, and:
2. Tell it to "set line /share tt:".

This might also work with ALL-IN-1 (Section 2.2).

[ C-Kermit ] [ Kermit Home ]

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3. COMMUNICATIONS

SECTION CONTENTS:

  3.1. Serial and LAT Communications
  3.2. Network Communications

Also see:

• Section 6 of the Installation Instructions: Using Modems by Richard B. Gilbert.
• http://www.tmesis.com/modem/.

3.1. Serial and LAT Communications

SUBSECTION CONTENTS:

  3.1.1. Dialing
  3.1.2. Speed
  3.1.3. Echoing
  3.1.4. Modem Signals
  3.1.5. Buffering and Flow Control
  3.1.6. LAT

If you are experiencing very poor performance on serial connections, use the VMS command SHOW TERMINAL to make sure that the terminal device has the DMA (Direct Memory Access) characteristic. If it does not, try setting it (or get your system manager to, in case privilege is required):

  $ SET TERMINAL device_name /PERMANENT/DMA

On some slower VAX models with built-in serial ports, such as the VAXstation 3100 or MicroVAX-II, receiving files on serial ports at (say) 19200 bps results in high CPU utilization, slowing down the system for other processes. This is because on certain systems, such as the VS3100, serial ports interrupt the CPU every time a character arrives. Most VMS systems nowadays, however, support either DMA for serial port i/o, or have their users coming in through terminal servers.

3.1.1. Dialing

  $ SET TERMINAL TTA0 /MODEM /PERM

Dialing is possible only on LAT devices and on serial ports that have that have the /MODEM attribute (e.g. "set term tta0 /modem /altypahd /perm"). The modem must be configured for "DSR tracks CD" -- that is, it must not turn on its DSR signal before the connection is made; otherwise VMS will hang up on it during the dialing process. C-Kermit 7.0 and later include "&S1" in the initialization string for modems that use the AT command set. If you are modifying init strings or defining your own modem type, be sure to include this command or the equivalent.

If a DIAL or SET SPEED command gives the error:

  ?ttbin: sys$qiow: %SYSTEM-F-NOLOG_IO, operation requires LOG_IO privilege

then either the user must be given LOG_IO privilege or else the device must be given the SET_SPEED attribute. However, note that under certain versions of VMS the TT2$M_SETSPEED bit in TTY_DEFCHAR2 is not properly propogated to LAT devices. It is best to issue the command SET TERM/PERM/SET_SPEED LTA31: at startup when the LTA31 device is initially created (which, of course, would be done by a sufficiently privileged account).

"How do I dial with C-Kermit and then exit, leaving the connection open so I can use it from another application?" Prior to starting Kermit, tell VMS to set the device to /NOMODEM. Another possibility is to allocate the line BEFORE you run C-Kermit. Ownership is defined as either having a channel assigned to the device or having allocated the device. All the channels get closed when the image exits, but allocation persists.

3.1.2. Speed

3.1.3. Echoing

3.1.4. Modem Signals

  3.1.4.1. The SET CARRIER-WATCH Command
  3.1.4.2. The SHOW COMMUNICATIONS Command
  3.1.4.3. The WAIT Command
  3.1.4.4. The HANGUP Command

A VMS serial communication device has either the /MODEM or else the /NOMODEM characteristic. You can view a device's configuration with the VMS SHOW TERMINAL command, for example:

  $ SHOW TERMINAL TTA0:

and you can change it with SET TERMINAL, e.g.:

  $ SET TERMINAL TTA0: /MODEM

When a /MODEM device is opened (e.g. with C-Kermit's SET LINE command), VMS asserts the DTR signal (assuming the interface and cable support modem signals), and allows I/O with the device even if the device is not asserting the CD signal. However, once the device does assert CD (or, perhaps more accurately, whenever the phone is "off hook"), VMS requires CD to stay up for further I/O; if the CD signal goes off, VMS returns a hangup (SS$_HANGUP) indication.

When a /NOMODEM device is opened, VMS does not assert any modem signals, including DTR, and does not require or test for any modem signals from the device. Thus the /NOMODEM is of little use with any kind of data communication equipment (e.g. modems, terminal servers, multiplexers) that require DTR (some modems can be configured to ignore DTR, e.g. with AT&D0).

On the other hand, /NOMODEM is probably necessary for VMS serial ports that do not support modem signaling (such as the one on the VAXstation 3100), or cables that do not contain all the needed wires (such as DEC's MMJ connector; looks like an RJ45 modular jack, but with an offset tab). If you use a /NOMODEM port, the device it is connected to must be configured to operate without seeing DTR, and in any case C-Kermit will not be able to detect connection loss.

Setting /MODEM or /NOMODEM on a LAT device has no effect on the LAT port itself, nor, evidently, on VMS -- reportedly, SS$_HANGUP is still reported when the LAT device hangs up, even when set to /NOMODEM.

Although it is within the power of an application such as C-Kermit to switch the device between /MODEM and /NOMODEM, it is not practical because doing so hangs up the device. Thus C-Kermit lets the VMS terminal driver control the modem signals, and interprets and reacts to indications about modem signals from VMS as best it can, according to your preferences.

3.1.4.1. The SET CARRIER-WATCH Command

When CARRIER-WATCH is OFF, the aforementioned checks are not made, and any SS$_HANGUP errors that occur are ignored.

If the device is set to /NOMODEM, all checks for carrier will fail, and the device will be unusable unless CARRIER-WATCH is OFF.

On LAT devices, the initial checks are never made since LAT devices do not reveal their modem signals to VMS. SS$_HANGUP errors, however, are treated as they are for real serial ports.

3.1.4.2. The SHOW COMMUNICATIONS Command

3.1.4.3. The WAIT Command

3.1.4.4. The HANGUP Command

If you use the HANGUP command on a /NOMODEM device that is, nevertheless, connected to a modem, be sure that Kermit has been told to:

  SET MODEM HANGUP-METHOD MODEM-COMMAND

3.1.5. Buffering and Flow Control

Setting the port to hardware flow control at the console will not have any meaning to VMS. It does not see or make use of that information. Also VMS does not officially support hardware flow control for serial lines. For output when using modem lines the system will honor CTS. But we will not lower RTS when the type- ahead buffer is almost full. In V7.1 there is an attribute to enable RTS for input flow control on modem lines. But this support is not documented and there is no way from DCL to enable it.

During terminal connection (SET LINE) and file transfer over a serial device, buffer-overrun or BYTLM-quota-exceeded messages might appear. It is essential that any VMS system that needs to use Kermit or any other program to transfer files over serial devices, especially when long packets or sliding windows are to be used, be SYSGEN'd with large typeahead buffers, and that user accounts be given large BYTLM quotas. See the Installation Instructions.

Note that LATmaster software (optional as of VMS V5.4-1, mandatory as of VMS V5.5) requires a minimum Alt-Typeahead buffer of 2064 bytes. Thus, you may already have increased the size.

To get around problems on systems where users have small BYTLM quotas, the txbufr() routine in CKVTIO.C has been limited to reading 512-byte chunks at a time from the communication device. This does not appear to have an adverse affect on performance. If it does, a quick fix is to recompile CKVTIO.C, defining CKV_IO_SIZE to be something bigger, e.g.

  /define=("CKV_IO_SIZE=8192")

or whatever. A better fix might be to have txbufr() check the user's remaining BYTLM quota before doing each read. But the overhead in doing this might cancel out the advantage of doing it.

The SET FLOW RTS/CTS command is not supported in the VMS version of C-Kermit. VMS versions prior to 7.0 do not support RTS/CTS (hardware) flow control. However, RTS/CTS flow control can still be used on LAT ports that support it.

VMS flow control is governed by two SET TERMINAL parameters: /TTSYNC and /HOSTSYNC. TTSYNC lets the terminal control the flow of data from the host and HOSTSYNC lets the host control the flow of data from the terminal. In general, these are implemented as Xon/Xoff flow control in each direction, but on LAT and TCP/IP connections, they can also affect the internal networking protocol, and they can be implemented on the LAT server's serial interface with any flow control method at all - Xon/Xoff, RTS/CTS, etc.

In VMS C-Kermit, SET FLOW XON/XOFF is equivalent to $ SET TERM /HOSTSYNC /TTSYNC. There should never be a reason to SET FLOW NONE in VMS -- in fact, it is almost always a bad idea (see File Transfer section).

When C-Kermit is in "remote mode", i.e. it is on the far end of a connection, and is not establishing a connection itself, it uses your current VMS SET TERMINAL parameters for flow control during command processing. During packet mode, however, it obeys your C-Kermit SET FLOW-CONTROL setting to ensure the chances of lost data are minimal.

When C-Kermit is in "local mode", i.e. it is being used to establish a connection with SET LINE or TELNET, there are two components to your connection: the part between your terminal and C-Kermit (call this "Part A"), and the part between C-Kermit and the remote computer or service that you have connected to ("Part B"). At all times, the flow control used on Part A is governed by your VMS SET TERMINAL parameters, and the flow control used on Part B is always governed by C-Kermit's SET FLOW-CONTROL command.

If you are using C-Kermit in local mode to access a remote host to use the EMACS editor, you might find that the Ctrl-S (Search) and Ctrl-Q (Quote) commands don't work -- your screen and keyboard "freeze" when you type Ctrl-S, and Ctrl-Q seems to have no effect (except unfreezing your session after Ctrl-S). This means that your VMS command terminal has the /TTSYNC characteristic; Ctrl-S and Ctrl-Q are being used for flow control between your terminal and the VMS system -- the remote system and EMACS never see them. There are two ways around this problem:

1. Tell VMS to SET TERM /NOTTSYNC before starting C-Kermit. In this case, you are in danger of losing data on the connection, particularly if your connection to VMS is through a LAT device.

2. Leave the /TTSYNC characteristic in force and use the long forms for the EMACS commands: ESC-X Search-Forward and ESC-X Quoted-Insert. Or assign these functions to other EMACS keys in your EMACS initialization file.

3.1.6. LAT

If you use C-Kermit to SET LINE to an LTA device and receive a hangup message immediately:

  contti: ttiosb.status: %SYSTEM-F-HANGUP, data set hang-up

then:

• Perhaps the line is already being used on another system that is connected to the same terminal server (in this case SET HOST /DTE will fail the same way). Unfortunately LAT has no way to signal this condition.

• Make sure you've created an LTA port on your VMS system which is mapped to the DECserver port that the modem is connected to.

• Can you use the VMS SET HOST/DTE command to connect to that line? If you get the same error (which you should) there's a configuration problem in the DECserver setup for that port, or the devices protection, or your privileges or quotas, or somesuch.

• In order for VMS to connect to the dial-out modem, it needs to see the carrier detect signal asserted. If that signal isn't asserted, the server will return a "hangup" error on the first character sent to the port. C-Kermit's SET CARRIER command has no effect in VMS.

• Additionally, some modems want to see various settings on RTS/CTS and DSR/DTR before they will accept input. If you have a breakout box and someone who is skilled at using it, you can usually resolve these problems.

C-Kermit puts LAT terminal servers into PASSTHRU mode, which disables their forward/backward session switch characters.

Reportedly, if you have CONNECTed out through a LAT device, the CONNECT-mode escape command to hang up (<esc-char>U) does not work. Reason: unknown. Cure: unknown (The LAT programming interface is very poorly documented). Workaround: SET LINE <cr> or CLOSE <cr> to close the SET LINE device.

Reportedly, although Kermit can SET LINE to a LAT device and work OK, the same can't be said for a "LAT group" (whatever that is). The user who submitted this report said that this problem could be worked around by telling VMS to SET TERM <blah> /NOALTYPEAHD before starting Kermit (take this one with a grain of salt).

Reportedly, to use C-Kermit with a LAT device under LATmaster, the associated terminal device must be set /NOREADSYNC.

Reportedly, when transferring files TO a VMS system over a LAT connection (for example, from a PC equipped with PATHWORKS or SuperLAT and MS-DOS Kermit), packet sizes greater than 255 (some reports say 70!) cannot be used, irrespective of the VMS SYSGEN parameters regarding MAXBUF, etc. The problem seems to lay in the LAT protocol itself, or the particular implementation of it, whereby applications are not informed of -- and cannot find out -- limits on transmission. (And yet, others say they have no problems with file transfers over LAT connections, even with packet sizes greater than 1000.)

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3.2. Network Communications

SECTION CONTENTS:

  3.2.1. X.25
  3.2.2. TCP/IP

There is (as yet) no support for initiating connections over DECnet, nor for VAX/PSI. Certain types of TCP/IP are supported (including DEC TCP/IP (UCX), CMU-OpenVMS/IP ("CMU/Tek"), TGV MultiNet, Wollongong WIN/TCP or PathWay, Process Software TCPware); other types: not yet (e.g. Fusion).

3.2.1. X.25

3.2.2. TCP/IP

The TCPware version works correctly with TCPware versions 4.1-2 or later; earlier versions, such 3.1-3, have a bug that can result in failure of C-Kermit to make network connections, with a message like:

 ?contti: network sys$qio: %SYSTEM-F-IVCHAN, invalid I/O channel

Process Software recommends upgrading to the current TCPware release.

DEC TCP/IP (UCX) 2.0C and earlier, which runs only on VAXes, has a bug that prevents TCP port lookup by name from working as expected, so if you tell C-Kermit to "telnet blah" or "set host blah", you'll get a "Connection refused" error. If you don't specify a port, Kermit substitutes the service name "telnet" and then asks UCX to look it up; UCX finds it but erroneously returns a port number with its bytes swapped (e.g. 5888 instead of 23), and then Kermit tries to connect to port 5888 on the host; most hosts will refuse the connection; if they don't, you probably didn't reach a Telnet port anyway. The workaround is to include a port number (not name) in your command. Any of the following will work:

  set host blah:23
  set host blah 23
  telnet blah:23
  telnet blah 23

A patch was issued after C-Kermit 6.0.192 was released, adding the following command to VMS C-Kermit versions built on VAXes with UCX:

  SET TCP UCX-PORT-BUG { ON, OFF }

If you have UCX 2.0C or earlier, and C-Kermit won't make Telnet connections, tell it to:

  SET TCP UCX-PORT-BUG ON

In case your version of C-Kermit 6.0 does not have this patch, then use the workaround of specifying a port number.

The previous hint also applies when running UCX versions of C-Kermit under Wollongong or other TCP/IP products that have a UCX compatibility mode. If you get "connection refused", then include the port number in the TELNET or SET HOST command.

The UCX version of Kermit works on MultiNet systems too, because MultiNet automatically goes into "UCX compatibility mode" when a UCX application is run.

You can also use the non-network version of C-Kermit on a MultiNet system to make TCP/IP connections as follows:

  $ telnet/create foo.bar.baz.com
  Trying...
  TELNET session now connected to _NTY5:
  %DCL-I-ALLOC, _$4$NTY5: allocated

  $ kermit
  C-Kermit 8.0.209, OpenVMS AXP
  Type ? or HELP for help
  C-Kermit>set line telnet_nty
  C-Kermit>connect
  etc...

If you enter the VAX from elsewhere through a TELNET connection, and the VAX is running CMU-OpenVMS/IP, Fusion, or an early version of DEC TCP/IP (UCX), you might notice that file transfers into the VAX fail almost immediately. If this happens, it is most likely the result of small VMS typeahead buffers. See the Installation Instructions for how to increase typeahead buffer sizes, or work around the problem by telling VMS C-Kermit to ask for smaller packets, for example:

  C-Kermit>set receive packet-length 65  ; (Use the longest length that works)

When using the CMU-OpenVMS/IP TCP/IP transport, assign the system logical INET$SERVICE_TELNET_TCP to the telnet port as follows:

  $ DEFINE /SYSTEM INET$SERVICE_TELNET_TCP 23

This is only required if the -j option is used without specifying a port to use (e.g. -j host). If this logical assignment is not made using `-j host' option will fail with the error:

  %CKERMIT-E-FATAL, can't open host connection

The default port, hardcoded in C-Kermit, is 23. Another port may be specified using the -j option as `-j host:port'.

SET INPUT ECHO OFF seems to have no effect when given to VMS C-Kermit and the INPUT command is reading from the console terminal.

[ C-Kermit ] [ Kermit Home ]

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4. GENERAL FAILURES

General failures can sometimes occur for reasons beyond Kermit's control, many of them related to VMS system parameters or limits on the user or process: disk quotas, user pagefile quotas (AUTHORIZE parameter PGFLQUO), system pagefile space filling up, etc. See the Installation Instructions for details.

To increase a user's pagefile quota, tell AUTHORIZE to MODIFY username/PGFLQUO=number. The system itself might be running out of pagefile space, which would cause the system to grind to a halt and eventually crash. You can check the system pagefiles with SHOW MEMORY/FILE: add up the "Free" numbers for the [*]*PAGEFILE.SYS files and see if the total is big enough (there should normally be at least 100K free pages on an active system). If not, the system manager would use the procedure @SYS$UPDATE:SWAPFILES to resize the files.

VMS C-Kermit can hang or crash with an "access violation" under certain conditions when trying to hang up a modem-controlled device that is already hung up; investigation shows that the hang or crash happens in VMS kernel space, not in Kermit.

Reportedly, on certain VMS configurations (but not others), the following sequence can cause C-Kermit to crash:

  set host somewhere
  connect
  (escape back)
  receive
  Ctrl-C
  connect

The problem appears to be in the VMS C library's implementation of signal handling and longjumps.

"Zombie" process can be left behind under certain conditions when a VMS Kermit server has been sent a BYE command, particularly over a TCP/IP connection (connection disappears before VMS has a chance to print its "logged out" message, and now there is nothing to print it on).

One user reported "massive failures" when transferring files with VMS C-Kermit through a particular kind of terminal server. She had followed all the directions in the manual, the CKVINS.TXT file, and the CKVBWR.TXT files (as it was before this item was added). The terminal server, an Equinox ELG48, uses TELNET protocol to a DECstation 3000 Model 600 running VMS 6.1 and TGV MultiNet 3.3. Later, she reported: "It turned out that upgrading the software on our terminal server has fixed the problem. It's so odd that the problem only occured after we upgraded from VMS V5.5-2 to V6.1, since the terminal server worked fine before the upgrade. It's also weird that this terminal server has always worked fine for our Suns, also. Here's the details of the terminal server if you want to keep these details on file: Equinox PBX 20 with ELG 48 board. The ELG 48 rev was 2.30. After upgrading it to V2.33, everything works fine."

[ C-Kermit ] [ Kermit Home ]

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5. LOCAL FILE OPERATIONS

As of edit 190, VMS C-Kermit supports append operations: the various logs (packet, debug, transaction, etc) can be opened in append mode by including the APPEND keyword after the filename, e.g.:

  LOG TRANSACTIONS TRANSACT.LOG APPEND

An arbitrary file can be opened for output in append mode:

  OPEN APPEND OOFA.TXT

and the SET FILE COLLISION APPEND option now works during file transfer.

When using append operations:

• Be careful not to append files of different types together, such as a text file to an indexed file, or a fixed-record binary file to a text file, etc. The result will generally be unusable.

• SET FILE COLLISION APPEND does not work when the FILE TYPE is LABELED. This is deliberate: labeled transfers are designed to give you an exact copy of the file, including attributes.

C-Kermit 7.0 (Jan-Feb 2000) added a new stdio-based FILE command allowing opening, closing, reading, writing of local files. Since C-Kermit is a C program, this works best with stream files. In particular FOPEN /APPEND works only with stream (Stream_LF) files. If you try to use FOPEN /APPEND on a non-Stream_LF file, the appended portion is in Stream_LF format but the original portion remains in whatever format it was in before.

There is no facility in C-Kermit to distinguish between "overwriting" and "versioning". SET FILE COLLISION OVERWRITE always creates a new version in VMS.

BUG: As of this writing, APPEND operations do not use the RMS "first free byte", and so start on a new block boundary.

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6. FILE TRANSFER

SECTION CONTENTS:

  6.1. Automatic Transfer Mode
  6.2. Oddball File Formats
  6.3. Disk Quotas
  6.4. Control-Character (Un)Prefixing
  6.5. External Protocols
  6.6. Miscellaneous

Remember that VMS file formats are substantially different from those on UNIX, DOS, Windows, etc. Be sure to consult the VMS Appendix of "Using C-Kermit" on this topic, and to find out the special commands and procedures that apply to VMS.

C-Kermit 7.0 has the following problems, which we hope can be resolved before the final release:

• LABELED mode lacks relative pathname option; directory-tree transfers don't work between two VMS systems because they go into LABELED mode automatically (this one should be fixed in C-Kermit 7.0).

• Confusion about SET TRANSFER MODE { AUTOMATIC, MANUAL } vs FILE TYPE IMAGE (should AUTOMATIC unset IMAGE? Should IMAGE set MANUAL? ...)

• Need better error message for failure to receive a file in text mode that has lines longer than 32K, or else a way to recover when this happens, e.g. by breaking the long line.

C-Kermit 7.0 also enables proper transfer of fixed-length-record files with odd record lengths, and fixes problems with overstrike records in Fortran Carriage Control files. These fixes should go a long way towards eradicating the complaints about files that Kermit-32 could transfer correctly, but C-Kermit could not.

[ C-Kermit ] [ Kermit Home ]

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6.1. Automatic Transfer Mode

File transfer modes (TEXT vs BINARY) are set automatically for each file when sending. The SET FILE TYPE BINARY and SET FILE TYPE TEXT commands are ignored when sending files. So (in C-Kermit 7.0) are filename patterns (SET FILE PATTERNS). To force binary-mode transmission, use SET FILE TYPE IMAGE. See the VMS appendix of Using C-Kermit.

One notable consequence of this fact is that if you send a file from VMS C-Kermit in IMAGE mode (because it would not be transferred in binary mode without this setting), then any attempt to RESEND or REGET it must also be done with VMS C-Kermit in IMAGE mode.

The other aspect of automatic transfer mode is that VMS-to-VMS transfers shift automatically into LABELED mode (again, see the manual). One consequence of this is that any "as-name" that you give for the file is ignored. To defeat this, use "set transfer mode manual".

DEC PATHWORKS file services normally create files in stream mode, but this can be overridden when the file service is created:

  $ ADMIN/PCSA
  PCSA> SET FILE_SERVER SERVICE service-name/ATTRIBUTES=SEQUENTIAL_FIXED

The normal stream files will be treated as TEXT by Kermit. To transfer PATHWORKS files that are really binary, such as executables, use IMAGE mode.

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6.2. Oddball File Formats

When sending binary files that have an odd record length, please note that these files are actually stored with an even record length on disk. For example, suppose DIR/FULL X.VDM says "fixed-length records, record length 17". On disk, the file really has 18-byte records; each 17-byte record is padded with a NUL (0) byte to make its length even; this is revealed by DUMP. Prior to version 7.0, C-Kermit sent the raw records, INCLUDING THE PADDING. In 7.0 and later, odd-length records are sent without padding.

If a text file is accidentally sent to VMS C-Kermit in binary mode, you can fix it afterwards (in recent VMS versions) with a DCL command like:

 $ SET FILE/ATTRIBUTES=(RFM:STM,LRL:0,MRS:0) filename

Transfer of VFC (Variable with Fixed Control) files, such as those created by DCL, is problematic, since the meaning of the control bytes is defined by the application.

VMS MAIL messages: If you want to download mail messages to a PC (or other non-VMS system), select the message of interest using the SELECT and DIRECTORY commands within VMS MAIL, then EXTRACT/ALL to extract all the selected messages to a normal text file, then use Kermit to SEND this file. Don't even think about trying to transfer your mail file as-is to a non-VMS system; it is a complicated indexed file, possibly containing pointers to other files, etc.

ZIP files: If you have trouble transferring ZIP files into or out of VMS using BINARY mode, use IMAGE mode instead (SET FILE TYPE IMAGE). The same applies to binary files created by VMS UNZIP.

[ C-Kermit ] [ Kermit Home ]

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6.3. Disk Quotas

Incoming files are rejected if the available space on the disk device is less than the size of the file. However, the user's disk quota is not checked. Quota checking could erroneously report that a user couldn't store a file for a number of reasons: for example, the user has the EXQUOTA privilege, C-Kermit is installed with EXQUOTA privilege (not recommended!), overdraft, etc. Because of the large potential for denying a transfer that would fit, the file is accepted regardless of the disk quota. This is consistent with the way other VMS utilities work.

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6.4. Control-Character (Un)Prefixing

Exercise caution when sending files to VMS when C-Kermit is in remote mode. Aside from all the buffering limitations of LAT and VMS, please note the following:

• On most VMS systems, the controlling terminal MUST have the /TTSYNC and /HOSTSYNC characteristics, even on Telnet connections, or else massive amounts of data can be lost.

• There are evidently certain control characters that can not be safely unprefixed when sending to VMS, no matter how far C-Kermit goes to put the job's controlling terminal in "passthrough" mode. These include:

    Ctrl-Q  XOFF  17
    Ctrl-S  XON   19
    Ctrl-C  ETX    3
    Ctrl-N  SO    14
    Ctrl-O  SI    15
    Ctrl-X  CAN   24
    Ctrl-Y  EM    25
  

As well as 141, 145, 147 (CR, XOFF, XON with their high bits set). If you find file transfers into VMS stalling, it is very likely because one or more of the these characters is unprefixed.

On a related note, Carriage Return (13) and IAC (255) must be prefixed on Telnet connections, and Kermit's start-of-packet character (normally SOH, ASCII 1) should also be prefixed. NUL (0) should be prefixed too.

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6.5. External Protocols

You can use the ZMODEM SZ and RZ commands as "external protocols" over a connection you have established with C-Kermit, to a host or service that does not support Kermit protocol. Start the file transfer on the remote end, escape back to C-Kermit, give the SPAWN command, and then (for example):

  $ define tt xxx:
  $ rz

where xxx is the designation of the terminal device (TT or LTA) that you have dialed out on. When the transfer is complete, LOGOUT from the SPAWN'd subprocess and you'll be back at the C-Kermit prompt.

[ C-Kermit ] [ Kermit Home ]

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6.6. Miscellaneous

The file size shown in the file transfer display when sending a file might be incorrect under certain conditions (but the file is still transferred correctly).

Incoming files, if accepted, are always stored as a new file with the next highest version number, even when FILE COLLISION is set to OVERWRITE or RENAME.

When you send a BYE command to a VMS C-Kermit server, it does not guarantee that the VMS job will be logged out. If C-Kermit was SPAWN'd from another process, only C-Kermit itself disappears in this case. Even if the whole VMS session ends, if the user came in through a LAT terminal server, they will be back at the "Local>" prompt and the phone line won't be disconnected.

When transferring files in LABELED mode, the file transfer display shows the name the file was sent as, not the "true" name within the labeled file. Also, note that a transfer may fail with an obscure error (can't create output file) if there is something incorrect with the label information (for example, if you specified that the file should be restored to the original directory and you don't have privilege to write to that directory on this system).

Reportedly, when VMS C-Kermit is in local mode and transferring a file (file transfer display is showing) over a MultiNet TCP/IP connection and a broadcast from a completing batch job (SUBMIT/NOTIFY) arrives, it crashes C-Kermit with %SYSTEM-F-ACCVIO, access violation. The stack dump shows this occurs in the netinc() routine while reading a packet (rpack).

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7. OTHER TOPICS