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CKCKER.BWR "Beware File" for C-Kermit Version 5A -*- text -*- Applies to 5A(189) Last update: Wed Jun 30 10:08:36 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. 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 specified file does not exist or cannot be opened, no error message is printed. If you enter control characters, space, or question mark into a command preceded by the command-quote character, backslash (\), the backslash disappears and is replaced by the quoted character. If the quoted character is a control character, it is displayed as a circumflex (^). This allows editing (backspace, delete, Ctrl-W, Ctrl-W) to work correctly. If you quote special characters in a filename (e.g. in the SEND command), filename completion may appear 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 (note: this can easily 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 quote the semicolon, for example: C-Kermit>ask \%a { What? } What? this text ; includes a comment character C-Kermit>echo \%a this text C-Kermit>ask \%a { What? } What? this text \; includes a comment character C-Kermit>echo \%a this text ; includes a comment character C-Kermit> 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. C-Kermit gives a few other tricks to make it easier on the end-user (if not on the script programmer). For example, you could write a macro like this to let users enter their text enclosed in doublequotes if they want to preserve leading and/or trailing spaces (in which case the macro trims the quotes): ; Define a macro XASK to prompt the user for some text and to ; keep the leading and trailing spaces if the user encloses the text ; in doublequotes... Argument \%1 is the ASK prompt. Variable \%9 ; is a local variable used to hold and return the response. ; define xask ask \%9 \%1, - if eq \fright(\%9,1) " if eq \fsubstr(\%9,1) " - assign \%9 \fsubstr(\%9,2,\feval(\flen(\%9)-2)), - return \%9 ; This shows how to use the macro. ; Type Ctrl-C to get back to the prompt. :loop assign \%a \fexecute(xask {{This is the prompt: }}) echo [\%a] goto loop This gives results like: This is the prompt: abc xyz [abc xyz] This is the prompt: abc xyz [abc xyz] This is the prompt: "abc xyz" [abc xyz] This is the prompt: " abc xyz " [ abc xyz ] 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 does not function correctly. Example: C-Kermit>define first return 1 C-Kermit>first C-Kermit>echo \v(return) return <--- This should say "1" rather than "return" C-Kermit> Cause and cure are unknown. 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. 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) SET DIAL SPEED-MATCHING OFF C-Kermit knows about a large number of modems, depending on how it was built (type "set modem ?" to see the supported modem types; type "show features" to see any specific modem-related configuration options). This knowledge is imbedded in the SET MODEM and DIAL commands. If you are having trouble dialing your modem: a. SET DIAL DISPLAY ON to watch the dialing interactions between C-Kermit and your modem. b. Make sure you have given the SET MODEM <name> command BEFORE you issued the SET LINE and DIAL commands, and make sure that the modem name that you specified corresponds to the actual modem that you are trying to use. c. Make sure you have given a SET SPEED command to connect to the modem at a speed it supports (like 2400), AFTER you gave the SET LINE command. d. If that doesn't work, give the command SET DIAL MODEM-HANGUP OFF and try again. e. If that doesn't help, Give the command SET DIAL HANGUP OFF and try again. f. If that doesn't work, give the command SET CARRIER OFF and try again. g. If that doesn't work, maybe your modem is configured incorrectly. Use SET DIAL INIT-STRING <text> to have C-Kermit send the proper configuration commands to the modem at the commencement of dialing. h. Check the hardware configuration of your modem, and check the cable that connects your modem to your computer. 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 some situations the transfer rates achieved under these conditions may be 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. The SET DIAL MNP-ENABLE command only works for Telebit modems. It is OFF by default, to prevent (a) loss of incoming data after successful connection to a non-MNP modem, and (b) transmission of garbage characters to the remote host when the answering modem is not MNP capable (which can ruin automatic speed detection, login processes, script program execution, etc). See Telebit section for details. 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 that the modem's Command Line Terminator (S3) is set to 13 (carriage return). If it is not, C-Kermit's dialog with the modem might not 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 are incompatible with each other, 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 (which is the default), C-Kermit will change its interface speed automatically according to the speed reported in the modem's CONNECT message; when it is OFF, C-Kermit does not change the 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". FLOW-CONTROL versus dialing: 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. Several cautions are needed here: . 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 will 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 you have mapped them to. - If you SET your TERMINAL CHARACTER-SET to anything besides TRANSPARENT, C-Kermit translates your keystrokes (after applying any SET KEY definitions) before sending them to the remote host, and translates the characters received from the remote host before sending them to 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. The SET KEY command (except in OS/2) does not allow a key definition to be (or contain) the NUL (\0) character. 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. 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. 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. The message should be issued immediately, and protocol mode should not be entered (that is what zchki() is supposed to ensure!). If a fatal error message is to be issued during protocol mode, it should come in an E-packet. 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, notably a certain popular commercial package, claim to implement sliding windows, but do not do so correctly. 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 only to the nearest 2 seconds. This can cause update operations to send more files than necessary. SET FILE COLLISION OVERWRITE is risky, use it with caution. 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 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. SCRIPT PROGRAMMING 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. 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)