ZCOMM User Manual

 


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        7.17  Prometheus ProModem 1200


        The following switch setting works with ZCOMM: 1-4,6,9 on; 5,7,8,10

        off.[4] A custom "dial" script can be written to operate this modem in

        its native mode.



        7.18  Racal-Vadic Maxwell 2400V


        The Maxwell 2400V has long delays designed to allow switching between

        data and voice operation on the same phone line.  Unfortunately, they

        slow normal data operations.  The 2400VP reportedly does not have this

        feature.


        Use the default mm224 dialing routine discussed above for this modem.



        7.19  Standard 103/212


        The supplied "dial" script will present the number to the user and

        wait for a success/fail response if the mprefix string parameter is

        set empty.  Alternatively, one could change the script to loop waiting

        for carrier detect while the keyboard is inactive.  The Data Set Ready

        (DSR) signal may be connected to the modem's speed detect output (high

        for 1200 bps, low for 300) allowing the dr test condition to sample

        the DSR line to determine the speed of the incoming call.



        7.20  Data Race BMX


        These modems have a switch selected interface speed, an AT style

        command set, and switch options for software or hardware flow control.

        Recommended settings are: AT commands, Dialup, 8 bit data (down),

        disable XON (7 and 8 down), Echo on.  ZCOMM's handshake on command

        should be used.



        7.21  Strange Modems


        Most intelligent modems can be commanded to autodial with a suitable

        mprefix and msuffix string.  Those modems that won't work with a

        particular mprefix can be programmed with a custom "dial" script.  If

        the modem can be configured to reset to a known condition when DTR is



        __________


         4. Prometheus mode does not work with ZCOMM's built-in dialing

            software because the "DIAL COMPLETED" message makes ZCOMM think

            it's seen "CONNECT" (ZCOMM looks for a "T").




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        turned off, programming is usually straightforward.


        Otherwise, the script must determine what speed the modem is set to,

        and then,  at its present speed, command the modem to change to the

        desired speed.  The essential requirement is to write a script that

        controls the modem and responds to its state.  The information on

        scripts in Chapter 99 should prove useful.



        7.22  Manual Dialing with Smart Modems


        Some hotels and exotic locales sport telephone systems with unusual

        dialing requirements.  It may be necessary to dial the call with the

        telephone, talk to an operator, and then activate the modem.  With

        Hayes compatible modems, an ATD command may be given to the modem to

        connect it to the line and attempt a data handshake.



        7.23  Direct Connection


        ZCOMM works well communicating with locally connected microcomputers,

        minicomputers, or mainframes with direct RS-232 connections.  For such

        applications, only transmit and receive data data lines need be

        connected to the computer.  The Carrier Detect line[5] should be

        driven ON (+5 volts) to prevent noise on this line by strapping it to

        Data Terminal Ready [6] if no other signal is available.


        For best high speed operation, replace 8250 or 16450 UART chips with

        the NS16550AN chip.  ZCOMM enables the hardware buffering on this chip

        to avoid data loss caused by TSR programs, special device drivers,

        extended memory disks or caches, and DOS clock interrupts.















        __________


         5. Pin 8 on 25 pin RS-232 connector, pin 1 on PC-AT 9 pin connector.


         6. Pin 20 on RS-232 connector, pin 4 on PC-AT 9 pin connector.




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        8.  YOUR TELEPHONE DIRECTORY


        ZCOMM's telephone directory is a big flexibility advantage over

        traditional communications programs which require one or more separate

        files for each system called, or limit directory information to little

        more than a telephone number.


        The telephone directory is a plain ASCII text file which can be edited

        with standard text editors (brief, teco, EMACS, edlin, etc.).

        Normally, ZCOMM expects to find the telephone directory in the file

        /PHODIR.t on the current disk.  The pathname may be changed with the

        PHONES environment variable.  Forward slashes should be used to

        indicate directories.


        EXAMPLE: C>set PHONES=c:/yam/lib/PHODIR.t



        EXAMPLE: $ PHONES=/u/flashg/bin/phones.t; export PHONES (for Unix)



        The putsnp program may also be used to change ZCOMM's default

        Telephone Directory pathname.


        The call command connects to another computer.  When you give a

        call name command, ZCOMM prepares for a modem call and then searches

        the telephone directory file for a line starting with name.


        It is not necessary to type the entire name as it appears in the file.

        ZCOMM will find the first entry that name is a prefix of.


        EXAMPLE: call cis would access either the cis300 or cis1200 telephone

        directory entry, whichever was first.


        When using two entries with similar names (such as "cis300" and

        "cis1200"), place the favorite entry first.  This way you can just

        type call cis to get the desired entry.


        If the search is successful, the call command copies the complete

        directory entry name to the remote string parameter, where it can be

        used for log entries and automatic password generation.  ZCOMM

        executes the commands on the rest of the line (if any), and on

        succeeding lines beginning with a space or tab, until the next

        Telephone Directory entry or a return command is seen.


        There is no arbitrary limit to the size of the telephone directory.

        Popular entries may be placed near the front to minimize searching

        time.  When desired, Scripts can be placed in separate files

        referenced with a source command from the Telephone Directory entry.






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        8.1  Customizing Your Telephone Directory


        8.1.1  TAKE A SHORTCUT WITH PHOMAST.T  This starter script was written

        by Michael Ash of San Antonio, Texas.  It is easy to configure and use

        by following the detailed instructions included in the file itself.


        8.1.2  CUSTOMIZING PHONES.T  Compared to phomast.t, phones.t is the

        "industrial strength" prototype directory.  While not as easy to

        configure as phomast.t, it is powerful enough to tame a TrailBlazer

        and other complex modems.


        When ZCOMM begins execution, it searches the telephone directory for

        the setup entry.  (A directory entry has the entry name starting at

        the left margin.)



        The setup telephone directory in the distributed phodir.t file invokes

        a demonstration menu.  Once you have exercized the various

        demonstration possibilities, search for the xsetup telephone directory

        and change it to setup be removing the "x".  This will blank out the

        oroginal setup entry which appears later in the file.


        setup     port 1


        The first line of the "setup" entry selects port 1.


             : if !c speed 1200 putw "ATZ\r"


        This line is commented out with a colon (:).  If the colon is removed,

        the speed is changed to 1200 and ZCOMM sends an initialization command

        to the modem if no carrier detect signal is present.  If a carrier

        detect signal is present (modem still connected to the remote

        computer), the speed is not changed, and no initialization command is

        sent to the modem.


             pd1; pz480


        enables incoming time/date information provided by the ZMODEM and True

        YMODEM protocols.  Time/date stamping of transmitted files provides

        many advantages over traditional protocols, including the ability to

        selectively transmit files if the source file is newer than receiver's

        copy.  The number in the pz480 command should represent the local time

        zone expressed as minutes behind GMT.[1]


        This line should be commented out with a leading colon (or removed) if



        __________


         1. Pacific Standard Time is 480 minutes behind Greenwich Mean Time




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        you use a backup program that depends on the dates of files to

        determine which to save.


             set mprefix "ATDP"


        sets the string parameter mprefix to ATDP, setting the Hayes modem to

        use rotary (pulse) dialing.  If your phone uses tone dialing, comment

        that line out (place a leading colon to make ZCOMM pass over it) and

        uncomment the line containig "ATDT".


             set l "1"; set m "1"


        The l and m string parameters support the dynamic selection of one or

        more ALDS alternate long distance carriers.  The default values for

        these parameters is the digit 1.


        When making entries in your telephone directory, use %l- for numbers

        with different area codes, and %m- for numbers with the same area code

        as yours.


        If you use a long distance credit card or sometimes dial out from

        hotel or PBX lines, be sure to modify the att, ddd, hotel9, and hotel8

        telephone directory entries in phones.t to suit your needs.


        The set command sets the string parameter l (lower case L) to 1

        (number), providing for normal long distance access.  If you have an

        alternative long distance service, set this parameter to the required

        access string for that service.[2] The "set m 1" command sets the

        string parameter m to 1, providing for normal long distance access for

        numbers in your same area code.  If you have an alternative long

        distance service, set this parameter to the required access string for

        that service, plus your area code if required. (Some alternate long

        distance services require the area code for all calls, even those in

        your own area code.)


             set answerback "YOUR NAME CITY\r\n\21"


        Change the answerback setting to reflect your name.[3] Be sure to keep

        the \21 at the end of the string.[4]


        The next lines configure soft keys F3 to FS4.  Their functions are



        __________


         2. Use the "setsavenet" entry in PHODIR.t as a prototype.


         3. Some timesharing systems may require a specific answerback string.


         4. See Chapter 25 for a description character escapes.




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        described at the end of Chapter 18.


             : display bell=visual


        Causes bell characters to be displayed as a flashing musical note

        instead of sounding.  If you want a silent bell, uncomment this line.


             set quitcmd "\003\336off\r"


        This string is sent to the remote before disconnecting when an ALT-Q

        is typed during a protocol file transfer.


             : set calllog c:/calllog

             : set rxlog c:/tmp/rxlog

             : set txlog c:/tmp/txlog


        The above lines set the pathnames for logs of calls, files received,

        and files transmitted.


             set f10 "@help"

             if fyamhelp.t set helpfile "yamhelp.t"

             if f/umanh.hlp set helpfile "@yhp /umanh.hlp"

             if fumanh.hlp set helpfile "@yhp umanh.hlp"


        The above lines locate the help file and program F10 to summon the

        help processor if available.  These lines may be changed if you keep

        these files in other directories.


             : if dc ps4 pn2 pr97


        If a color display is used on DOS, uncommenting this line selects red

        status line (ps4), green normal text (pn2), and a blue/yellow for

        reverse video (pr97).  These colors may be more suitable than the

        default black and white.  Another possibility is "pn3" which selects

        blue-green for normal text.  You may wish to experiment with these

        values to find ones best suited for your particular combination of

        display equipment and visual preferences.  Changing the colors from

        time to time may prolong display tube life.  The colors Telephone

        Directory entry* displays the colors generated by the possible numeric

        parameter values:


        EXAMPLE: gosub colors


        Some programs, including the "DEC Store" demonstration, will not

        display exactly as intended with some combinations of the above

        display parameters.


        You may wish to keep your phone numbers etc.  in one file and relegate

        information specific to each computer to a separate file.  The setup

        entry in phones.t checks for the existience of a phones.ts file and

        executes it of found.



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             set s0 ""

             setc pho "%PHONES\&s";  if f%pho source %pho

             if %s0 return


        The supplied phones.ts file is used on Omen's 386 Xenix system, and

        may be used as an example.  On DOS, if you use VT100 emulation with

        keyboard mapping most of the time, you can add the contents of the

        keyboard mapping file std.mk, xen.mk, or 101.mk to your phones.ts

        file.


        While editing your telephone directory, you might wish to add some

        entries for your favorite systems in the same format used by the

        "amrad", "amsat", or "denver" directory entries.


        When the PHODIR.t file is ready, type "ZCOMM<ENTER>" to run ZCOMM.

        ZCOMM will print several lines of greeting and then silently execute

        the commands in the setup directory entry.


        If ZCOMM can't open PHODIR.t, exit ZCOMM with "x<ENTER>" and copy

        PHODIR.t to the correct directory, or set the DOS PHONES environment

        variable to the actual pathname (see Chapter 15).  Also check that the

        DOS CONFIG.SYS files contains FILES=20 to allow ZCOMM a sufficient

        number of open files for proper script operation.  If using DOS 3.2 or

        later, you may need to add a STACKS line to your CONFIG.SYS file, as

        described in Chapter 33.


        EXAMPLE: STACKS=20,128



























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        9.  HANDS ON TUTORIAL


        As a first order of business, run the demonstration program by typing

        ZCOMMDEMO at the DOS prompt.  The demo asks certain questions about

        your system, and then allows you to exercise a few of ZCOMM's features

        from a menu.  It's a good way to get a first "feel" for ZCOMM before

        getting down to business with the industrial strength software you

        will be using.


        Remember to turn off the CAPS LOCK key when running ZCOMM.


        ASSUMPTIONS: In addition to the minimum hardware requirements for

        ZCOMM, this tutorial assumes the use of a Hayes Smartmodem 1200 (or

        equivalent) connected to the COM1 port in accordance with the

        instructions in Chapter 7.  The tutorial assumes that ZCOMM.EXE,

        YHP.EXE, UMANH.HLP, and PHODIR.t are copied to the root directory of

        your working disk, and that ZCOMM.EXE has been serialized with the

        putsnp program.  If your system configuration is different, you will

        have to read the manual carefully to learn how to adjust for your

        configuration.


        After typing ZCOMM from the DOS prompt to load ZCOMM, type F10 to

        activate the flash-up help processor.  Browse through it to

        familiarize yourself with the information available via the F10 (help)

        key.


        To make a call without using a directory entry, type speed 1200 (or

        whatever) and then the phone number:


        speed 1200 123-4567


        The modem then dials the number.  When you are connected, ZCOMM will

        return to its command prompt.  Keyboard F2 to begin talking with the

        remote.  Give some commands to the remote until several screens' worth

        of text have scrolled by.


        Now press the PgUp function key.  The screen will now display text

        that had scrolled off before.  Use the PgUp, Home, PgDn, and End

        function keys to move around in the review buffer.


        Look for a moderately interesting nugget of wisdom, and use the up

        arrow and down arrow function keys on the numeric keypad to place the

        interesting part at the top of the screen.


        Hit "t" to set the top marker.  This causes all the text to display in

        high intensity.  Now move down using the down arrow key to place the

        first line of unwanted text at the top of the screen.


        Hit the "b" key to set the bottom pointer.  This will change the

        displayed text back to normal intensity.




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        Now hit "w" and ZCOMM will prompt for a filename to write to.  Type

        the filename followed by <ENTER>, and ZCOMM will write the selected

        data.  When the write operation is finished, the screen will redisplay

        the text.


        When you have the feel of it, type F1 to return to the term function

        and conversational connection to the remote computer.


        The demonstration disk circular buffer search/cut/paste menu choice

        demonstrates many of the review subcommands.


        Next, log off the remote computer.  When it drops the line, ZCOMM

        displays No Carrier Detect in reverse video to announce that the

        connection has been lost.  At this time you are still in the term

        function.


        Hit F1 to return to ZCOMM's command prompt.  Then type "off<ENTER>" to

        disconnect the modem and exit back to the operating system.


        Now is a good time to read the rest of the manual to discover the

        power of ZCOMM.  Chapter 9 presents some unusual sessions

        demonstrating more of ZCOMM's capabilities.


        9.1  Sample Sessions


                          Direct connection to COM2 at 19kb


         unix  port 2 speed 19200 source 101.mk; t

          |         |         |      |

          |         |         | Map keyboard, Invoke term function

          |         |         ___ Set 19200 bits per second

          |         ______________ Select port COM2

          _________________________ System name


                                Typical bulletin board


         rcpm   port 1 speed 1200 123-4567 t -8g

          |         |      |         |     |

          |         |      |         |     _ Term function, graphics

          |         |      |         _______ Number to call

          |         |      __________________ 1200 baud

          |         _________________________ Select COM1

          ____________________________________ System name


                               A Not so Typical Session


        The example below assumes a Hayes modem connected to a radio receiver

        tuned to the W1AW ASCII bulletins.  Refer to a recent issue of QST

        Magazine for a W1AW schedule.  to select the best signal.  Usually,

        the error rate is lowest when receiving a strong signal near the

        Maximum Useable Frequency (MUF).  Set the radio for Upper Sideband



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        (USB) reception.  Tune it so the resulting audio frequencies make the

        RD (Received Data) light turn on about 50 percent of the time.  Reset

        the modem by powering it down before attempting regular calls.


        w1aw speed 110 putw "ATS10=255 C0 H2 D\r" t -v

                 |                  |                |

                 |                  |        -v prints control chars

                 |                  |        as ^C so they won't

                 |                  |        erase the screen, etc.

                 |   Ignore Carrier Detect, Carrier Off, Special Off

                 |   Hook (Don't close relay), Originate, Online

                 |________ W1AW ASCII transmissions are at 110 bps


        A>ZCOMM call unix   Connect to a local system named unix

        jabber jabber ...   Login to system, change directory

        <ALT-2>Command:     Get a ZCOMM command prompt

        sz prg?.? prghlp.mm Upload some files

        jabber jabber ...

        sz *.c *.h          Download some source files

        Receiving ...       ZMODEM AutoDownload accepts them

        kermit -ix          Start the Unix Kermit server

        <F1>>>>c:           Get ZCOMM's command prompt

        remote dir          Get a directory listing

        Directory...        Directory listing on screen

        get f2              Get (fetch) a file

        f2 Open ...         File arrives

        send myfile         Send myfile to server

        finish              Finish server access

        t                   Enter term function

        kermit send f1      Start a Kermit file transfer

        f1 Open...          File is received AUTOMAGICALLY!

        jabber jabber ...   Log off local system

        <F1>>>>c:           Get ZCOMM's command prompt

        port 1              Select modem on COM1

        call rcpm           Dial a system called "rcpm"

        jabber jabber ...   Keyboarding with remote

        <Home>              Review function at top of text

        /to superhacker     Search for beginning of message to you

        t                   Set top pointer

        /to j. fred muggs   Search for beginning of next message

        b                   Set bottom pointer

        w                   Write selected text to a disk file

        <F1>                Return to term function

        E<ENTER>            Tell the rcpm to enter a message

        <ALT-2>Command:     Get a ZCOMM command prompt

        open -pt letter     Open "letter" and send to bbs, using

                            prompt and throttle modes to slow

                            transmission so the remote system won't

                            drop characters.

        dir                 Find out what files are on the RCPM

        xmodem s foo.bqr    Command RCPM to download a file



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        <ALT-2>Command:     Get a ZCOMM command prompt

        rc foo.bqr          Download a file with XMODEM/CRC

        PgUp PgUp ...       Flip back to the first part of

                            directory previously listed

        <ENTER>             Back to term function

        xmodem s dr.who     Download a critical file

        <ALT-2>Command:     Get a ZCOMM command prompt

        rc \misc\dr.who     Download the file

        jabber jabber ...   More keyboarding, logoff

        <F1>>>>c:           Get ZCOMM's command prompt

         Connect the modem to the radio's audio and tune in W1AW

        create rtty.tmp     Create a disk file for the bulletins

        call w1aw

        bleep twort sneep   Static on the radio - pure line hits until

                            W1AW is received while sending ASCII

        <F2>k               Review/k command clears the buffer

        QST DE W1AW ...

        END ... AR

        <ALT-C>             Close the capture file

        <F1>>>>c:off        Return to DOS


































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        10.  ACCESSING COMPUTER SYSTEMS


        10.1  Dialing


        Once you modem is interfaced per Chapter 7, you can connect to a

        remote system with the call command referencing an entry in your

        telephone directory.


        EXAMPLE: call kgbvax



        If a telephone directory entry has not been set up, TurboLearn(TM) may

        be invoked to dial a phone number and then learn your login procedure

        by keyboarding the F4 key.  You may choose to add the resulting script

        to your telephone directory, or retain it as a separate file acessible

        with the source command.  Please refer to the learn command in Chapter

        18.


        If you just want to call a number without ZCOMM learning anything,

        just type the telephone number from the command prompt already.[1]


        EXAMPLE: 123-4567


        When the modem connects, ZCOMM returns to the command prompt.  You can

        then keyboard the F2 key to connect your keyboard to the remote

        system.  If you wish to use "bulletin board graphics", use t -8g

        instead.


        10.2  Telenet/PC-Pursuit


        For best results, identify with D1 when Telenet asks for your terminal

        type.  This selection prevents the network from adding padding

        characters, which are just a waste of time with ZCOMM.


        To use XMODEM, YMODEM, Telink, and other traditional protocols on PC

        Pursuit, type


        SET 1:0,4:2,5:0,7:8,12:0


        after connecting to the PC-Pursuit target city.  This command prevents

        Telenet from "eating" control characters or breaking the connection

        when files containing certain patterns are transmitted.  This command

        disables Telenet's "<ENTER>@<ENTER>" escape.


        For ZMODEM or Sliding Windows Kermit a better alternatitive is:



        __________


         1. You may wish to add the /mnp modifier described in Chapter 7.




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        SET 4:2,5:1,12:1


        Please refer to Chapter 13 for network flow control considerations.


        10.3  Tymnet


        If using Tymnet, type Ctrl-R Ctrl-X just before the host computer name

        to enable software flow control with XOFF and XON characters.  "Half

        Duplex" may be activated with Ctrl-H.  Check with your network's

        documentation for further details or updates to this information.












































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        11.  FILE NAMES Good and Bad


        The pathnames of downloaded files must be legal PC-DOS file names as

        described in The File Specification in chapter 2 of the PC-DOS manual.

        When choosing file names, remember that PC-DOS does not distinguish

        between uppercase and lowercase characters in pathnames.


        The Compuserve-B, ZMODEM, YMODEM, and Kermit protocols use pathnames

        generated by the sending program.  File names transmitted from other

        systems may not be legal for DOS, or they may reference directories

        that cannot be created.[1]


        When ZCOMM receives a pathname from the sending program, ZCOMM first

        checks for the existence of a file with the same name.  If no such

        file is found, ZCOMM attempts to open the named file for writing.  If

        the file cannot be created because directories specified in the

        pathname do not exist, ZCOMM attempts to create the directories.  A

        pathname that cannot be opened for reading or writing is considered

        illegal.


        EXAMPLE: foo..bar is illegal for DOS because it contains two dots.


        An Illegal pathname is translated to name.NNN where name is the

        filename portion of the given file name restricted to 8 characters,

        and NNN is an assigned three digit number starting with 001 and

        incremented after each file download.  If a file with this new name

        already exists, the number is incremented up to 999, until a unique

        file name is found.  The open fails if a unique number cannot be

        found.


        EXAMPLE: A downloaded file with the name newprog.patch.1 might

        actually be downloaded as newprog.001.


        This check for illegal file names is made whenever ZCOMM attempts to

        create an output file.


        EXAMPLE: t foo.bar.baz given from the command prompt would invoke file

        name translation.









        __________


         1. A cirectory cannot be created if a regular file with the same

            pathname is present.




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        11.1  Pathname Translations


        Files affected by the dirrx, dircx and dirpx string variables have

        their directory paths and/or device specifier stripped if the string

        variable ends in a "/".  Otherwise a file specification with an

        absolute path overrides the string variable.  The pathname of the

        incoming file is checked before any of these transformations, allowing

        a host system to place all files received with a protocol in a private

        directory.


        EXAMPLE: C>set DIRRX=C:/download

        places files received with a protocol in the download directory on

        drive C unless the file specification included an absolute path or

        device letter.


        dirrx     File Stored Location

        (empty)   any  (same)

        C:/a f    C:/a/f

        C:/a /f   /f

        C:/a A:f  A:f

        C:/a/     f    C:/a/f

        C:/a/     /f   C:/a/f

        C:/a/     A:f  C:/a/f



        Parameter Affected commands

        dirrx     r{bcotwx7}, fget, get, bdump, usq, ZMODEM/Kermit

        AutoDownload

        dirsx     s{bctx7}, send, B protocol sends[2]

        dircx     create, t, message, private, >, bro/a

                  ap[d] (2nd argument)

        dirpx     review/w

        dirfx     f, open


        To show the possible pathname translations, consider the pathmame:

        A:/spy/kgb/sabotage/666 sent between two copies of ZCOMM with the

        ZMODEM protocol.


        The sending program command: sz A:/spy/kgb/sabotage/666 sends the file

        name 666.


        The command sz -f A:/spy/kgb/sabotage/666 sends the complete pathname

        /spy/kgb/sabotage/666.




        __________


         2. If the dirsx parameter is set, ambiguous or wild card file names

            cannot be used.




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        The command sz ONAME=hogwash A:/spy/kgb/sabotage/666 sends the

        pathname hogwash.


        sz PREFIX=C:/fbi/security/intelligence A:/spy/kgb/sabotage/666

        sends the pathname C:/fbi/security/intelligence/666.  Note that a disk

        identifier (C:) is being sent.


        On reception with ZMODEM AutoDownload or the rz command, the last

        example (C:/fbi/security/intelligence/666) would normally be stored

        under that exact pathname, creating the directories C:/fbi,

        C:/fbi/security, and C:/fbi/security/intelligence if needed.


        If the dirrx string variable had contained C:/downloads the incoming

        drive specifier would still have overidden the dirrx specification.


        If the dirrx string variable had contained C:/ollie/to_do/ the file

        would have ended up as C:/ollie/to_do/666 to the consternation of all.


        The command rz foobar could have been used to rename this file to

        foobar in the current directory.


        The oncloserx and onclosetx string parameters may be used to specify

        commands to execute after each file received or sent with file

        transfer protocols.  Their use is described in Chapter 12.






























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        12.  PROTOCOL FILE TRANSFERS


        With many different ways to transfer files with ZCOMM, your choice of

        file transfer methods could make the difference between efficient,

        error free data and slow or error prone transfers.  This chapter gives

        an overview of the different ways to transfer files with emphasis on

        their relative merits.


        A file transfer protocol should have high integrity (assurance of

        accurate data) and high robustness (low probability of aborting a

        transfer).


        The following subchapters discuss these file transfer methods in more

        detail.


        12.1  ZMODEM-90


        ZMODEM was developed for the public domain under contract by Telenet,

        a major packet switched network.  ZMODEM has been submitted to the

        ANSI X12C committee.


        ZMODEM-90(TM) is a refinement of ZMODEM with increased performance,

        reliability and compatibility with a wider variety of environments.


        ZMODEM provides a greatly simplified user interface.  The file name is

        entered once, and transfer options may be given to the sending

        program, even those that apply to the receiver.  ZMODEM

        AutoDownload(TM) allows menu and mouse driven programs to download

        files and commands with no extra keyboarding required.


        ZMODEM transfers one or more files with a single command.  The size

        and transfer time for each file is displayed, and the total number of

        files, size, and transmission time is displayed when more than one

        file remains to be sent on a command.


        Keyboarding ALT-F allows the receiver to bypass an individual file

        without having to restart the batch.


        ZMODEM transfers both files and commands.  Command download allows one

        of the computers to take positive control of the session.  A security

        challenge (activated by ZMODEM AutoDownload(TM)) guards against Trojan

        Horse messages.*


        ZMODEM file transfers preserve the file date and the exact file

        contents, unlike traditional protocols that append garbage to files.


        Streaming transmission provides full throughput over satellite links

        and packet switched networks.  One of three ZMODEM streaming control

        methods may be used with systems that allow the sender to monitor the

        received data for error correction packets without interrupting

        transmission.  ZMODEM's "block length" is the entire file!



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        Individually acknowledged packets support other systems.


        ZMODEM allows programs to adjust the protocol parameters for optimum

        efficiency as the file is being sent.  ZMODEM-90 allows programs to

        adjust character encoding for best results with a variety of systems.


        Some programs support ZMODEM compression for even faster file

        transfers under appropriate conditions with the Z file transfer option

        (q.v.).


        ZMODEM is immune to conditions that prevent reliable, accurate file

        transfers with traditional protocols:


         + ZMODEM data transfers are protected by the Federal Standard 32 bit

           CRC to assure reliable transfers.  This 32 bit CRC gives an

           undetected error rate five orders of magnitude better than XMODEM's

           16 bit CRC, and more than a billion times better than checksum

           XMODEM.  ZMODEM uses 16 bit CRC for file transfers with programs

           that do not support 32 bit CRC.


         + Most important, all ZMODEM protocol transactions are protected by

           CRC.  Other protocols advertising 16 or 32 bit CRC sometimes fail

           under stress because critical control messages are not protected by

           CRC.


        Omen Technology Inc's Intelligent Crash Recovery(TM) and advanced file

        management.  If you've ever been disconnected when a huge file

        transfer was almost finished, you'll appreciate resuming/recovering

        the file transfer with the ZMODEM r option.


        You can use the ZMODEM n option to transfer only those files that have

        changed since the last time they were transferred.  With the p option,

        you can unconditionally protect files that already exist on the

        destination system.  To update only the files you already have while

        skipping the rest, use the Yn options.


        To send a file with ZMODEM, the command sz file1 can be given from

        either the main command prompt, or from the term function via a

        secondary command prompt obtained with ALT-2.  Multiple files and wild

        cards may be used.


        EXAMPLE: sz file1 file2 *.lst



        12.1.1  ZMODEM AutoDownload  If Z mode has been enabled (the default),

        ZCOMM's term function will detect a ZMODEM transmission and receive

        the file(s) automatically, after a security check.  File transfer

        options for ZMODEM automatic downloads may be specified with the

        adlopts string parameter.


        The rz command may be also given from a command prompt.



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        Please refer to the sz and zcommand commands described in Chapter 18

        for examples and information.


        Rz and sz programs for Unix and VAX/VMS are available in rzsz.zoo.


        12.1.2  Tuning ZMODEM Parameters  Chapter 23.2 describes a number of

        ZMODEM numeric parameters which may be adjusted for extraordinary

        situations, or to fine tune the last 0.1 per cent of possible

        performance.


        The ZMODEM subpacket length (zmodem L parameter) and the ZMODEM frame

        length (zmodem l parameter) deserve special mention.  People tend to

        confuse these with the familiar 128 and 1024 byte block length used in

        XMODEM transfers.


        When a ZMODEM frame length of 0 is specified (the default), a single

        frame will span the entire file if there are no errors.  This is the

        main source of ZMODEM's reputation for fast transfers.


        Setting the ZMODEM frame length to a number between 64 and 16384

        restricts the frame length to that value.  At the end of each frame,

        the sender stops sending and waits for an acknowledgement from the

        receiver.  When set, the ZMODEM frame length corresponds in function

        to the 128 or 1024 byte block length of XMODEM based protocols.


        Each ZMODEM frame consists of one or more subpackets of 32 to 1024

        bytes.  Since the subpackets within a frame are sent without pause, a

        short subpacket length does not exact the terrible throughput penalty

        associated with short XMODEM and Kermit blocks.  In the absence of

        transmission errors, a 256 byte subpacket length has about two per

        cent more overhead than a 1024 byte subpacket length.  However, the

        longer subpacket length does increase error recovery time.


        ZCOMM dynamically adjusts the ZMODEM subpacket length on the basis of

        transmission speed and observed error rate.  If you know what the

        error rate on a particular call will be before starting a ZMODEM file

        transfer, setting the zmodem L numeric parameter will provide a small

        but noticeable improvement in performance, with 1024 best for clean

        lines and smaller numbers better for noisy lines.


        When sending files over noisy phone lines not involving networks, the

        speed of error recovery may be increased by decreasing the values of

        the ZMODEM t and p numeric parameters.


        Fascinating information about ZMODEM and other protocols is provided

        in ymodem.doc and zmodem.doc, part of yzmodem.zoo (yzmodem.arc).


        12.1.3  MobyTurbo  Standard ZMODEM escapes network control characters.

        This causes a slight drop in throughput when sending compressed files.

        When transferring compressed files over circuits that pass all 256 8

        bit codes, Moby Turbo(TM) may be used to optimize speed.  MobyTurbo



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        increases transfer speed without sacrificing ZMODEM flexibility or

        robustness.


        MobyTurbo is activated with the m option.  The m option may be used

        with the sz or rz command.


        EXAMPLE: sz -m *.zip


        MobyTurbo may be used with ZMODEM AutoDownloads by adding the m option

        to the adlopts string.


        EXAMPLE: set adlopts m



        12.1.4  Receiver Window Size Override  ZMODEM-90(TM) allows the

        receiver to specify the window size, with the Wn option, overriding

        the sender's window size.


        SEE ALSO: Wn option


        12.1.5  Almost 8 bit Environments  The e and m options may be used in

        conjunction with the xmtxesc and zmrxesc string parameters may to

        specify one or more control characters which cannot be passed over the

        serial line.


        SEE ALSO: zmtxesc, zmrxesc string parameters for details


        12.1.6  7 Bit Environments  ZMODEM-90 automatically detects 7 bit

        environments and adjusts accordingly.  When transferring files with a

        large number of bytes with the 8th bit set, the P ("pack") option may

        be used to optimize 7 bit encoding.


        12.1.7  Manual ABORT  If a ZMODEM transfer fails abruptly under

        exceptional conditions the program on the remote machine may be

        manually terminated by repeatedly typing Ctrl-X characters at it until

        the program exits.


        12.2  XMODEM Family Protocols


        12.2.1  TRUE YMODEM(TM)  Developed in 1981, YMODEM is finding its way

        into many communications programs.  With Omen's Enhanced Data

        Recovery(TM), YMODEM gives excellent efficiency, integrity, and good

        robustness in many applications.


        True YMODEM transfers one or more files in a batch, without alteration

        or added garbage characters.  True YMODEM also preserves the file date

        across multiple time zones.  ZCOMM and the Unix(TM) rb and sb programs

        preserve the file modification date.[1]






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        12.2.2  YMODEM-1k  The sb k option (1024 byte blocks) may be used to

        enhance throughput, especially when using timesharing systems,

        satellite links, or packet networks that can support the longer

        blocks.



        EXAMPLE: sb -k *.c *.h sends all .c and .h files in the current

        directory with 1024 byte blocks.[2]


        YMODEM and YMODEM-1k transfers can be received with the rb or F3

        commands.


        YMODEM file transfers with Unix and VMS systems are discussed later in

        this chapter.


        A few obsolete programs claiming to support YMODEM actually use XMODEM

        with 1024 byte blocks; use ZCOMM's sx -k and rc commands when

        necessary to exchange data with these non standardized products.


        12.2.3  YMODEM with OverThruster  YMODEM and YMODEM-1k file

        downloading from networks and timesharing systems is slowed by

        response times.  This slowing may be significant even when 1k blocks

        are used.  With some systems, one can speed up YMODEM downloads by

        using the o option with the rb command to receive the file.  Because

        OverThruster(TM) defeats error recovery, a line hit will usually abort

        a download.  OverThruster(TM) may be used with X.PC or MNP error

        correcting link level protocols.


        EXAMPLE: rb -o



        SEE ALSO: O numeric parameter


        12.2.4  XMODEM-1k  The XMODEM-1k protocol transfers one file per

        command with 1024 byte blocks and a nominal 16 bit CRC.  The file name

        must be entered for both the sender and the receiver.  Programs

        lacking ZCOMM's Cybernetic Data Recovery(TM) logic are less likely to

        transfer data accurately under marginal conditions.  XMODEM's use of

        every possible 8 bit code limit its effectiveness in many

        applications.


        The end of the file may be padded by up to 127 or 1023[3] garbage



        ______________________________________________________________________


         1. Controlled by the d and z numeric parameters


         2. ZCOMM switches to 128 byte blocks at the end of a file when the

            length warrants.




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        characters.


        To send a file with XMODEM-1k: sx -k file1


        To receive a file with XMODEM-1k: rc file1


        12.2.5  XMODEM-CRC (with fallback)  The XMODEM-CRC protocol transfers

        one file per command.  The XMODEM-CRC protocol requires the receiving

        program to initiate an XMODEM-CRC transfer.


        The file name must be entered for both the sender and the receiver.

        Even with CRC-16, programs lacking ZCOMM's Cybernetic Data

        Recovery(TM) are less likely to transfer data under marginal

        conditions.  XMODEM-CRC's short data blocks and use of every possible

        8 bit code limit its effectiveness in many applications.


        The end of the file may be padded by up to 127 garbage characters.


        To send a file with XMODEM (or XMODEM-CRC): sx file1


        To receive a file with XMODEM-CRC: rc file1


        12.2.6  Classic XMODEM  The original MODEM protocol, developed by Ward

        Christensen, is supported by a large and growing number of programs

        operating on a variety of micros and minis.  The base level XMODEM

        protocol gives good results when used over low error rate direct

        telephone connections.  XMODEM's short data blocks and use of every

        possible 8 bit code preclude its application in many environments.


        File transfers with this protocol add up to 127 garbage characters to

        transferred files.  The XMODEM protocol can transfer one file per

        command.  The file name must be entered at both the sender and the

        receiver.


        To send a file with XMODEM: sx file1


        To receive a file with Classic XMODEM: rx file1


        12.2.7  Relaxed XMODEM  ZCOMM's XMODEM and YMODEM support has been

        optimized for maximum reliability with a wide variety of systems under

        a wide variety of conditions.


        The default XMODEM and YMODEM timeout parameterss are "relaxed"

        timings.  They rarely need to be lengthened except under the most

        sluggish of conditions.  The zmodem t, T, and p numeric parameters



        ______________________________________________________________________


         3. Some programs (including ZCOMM) limit this padding to 127 bytes.




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        (q.v.) control timeouts for XMODEM, YMODEM, and ZMODEM.  The default

        values allow 10 seconds for a packet to appear and a 10 second pause

        within a packet before starting error recovery.


        EXAMPLE: zmodem pt200 pp150  :: Set more relaxed X/Y/ZMODEM timing



        For best reliability, Omen Technology does not recommend tightening

        these timings for XMODEM and YMODEM transfers on noisy lines.


        12.2.8  XMODEM with OverThruster  XMODEM file downloading from

        networks and timesharing systems is slowed by short blocks and long

        response times.  With some systems, one can speed up downloads by

        using the ro command to receive the file.  Because OverThruster(TM)

        defeats error recovery, a line hit will usually abort a download.

        With nearly error free connections, one can save enough time from the

        increased throughput to make up for the failed transfers.

        OverThruster(TM) may be used with X.PC or MNP error correcting link

        level protocols.


        EXAMPLE: ro file1



        EXAMPLE: rb -o



        SEE ALSO: O numeric parameter


        12.2.9  YMODEM-g: Traditional Overdrive  The proliferation of error

        correcting modems has sparked a proliferation of YMODEM-g programs,

        more and more of which actually meet minimal YMODEM protocol

        specifications.


        YMODEM-g transmits 0 or more files per batch with an ACK-less variant

        of YMODEM-1k.  The sender does not wait for individual data blocks to

        be acknowledged, allowing high speed transfers with error correcting

        modems.


        YMODEM-g assumes an error free communications channel.  A single

        transmission error or character lost because of DOS or TSR interrupt

        latency ruins the entire transfer, and YMODEM-g does not support Crash

        Recovery(TM).


        ZCOMM supports True YMODEM-g with the sb and rb -g commands.


        EXAMPLE: sb *.old Sends files in the current directory with YMODEM or

        YMODEM-g protocol.  The receiver controls whether YMODEM or YMODEM-g

        is used for the transfer.



        EXAMPLE: rb -g Receives with YMODEM-g protocol.



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        12.2.10  XMODEM Mutants Misrepresented as YMODEM  Despite continuing

        education efforts, a few lazy software providers insist on identifying

        their mutant XMODEM protocols as "ymodem".  They choose to ignore the

        definition of YMODEM that Ward Christensen wrote when he coined the

        term YMODEM in his April 1985 message:


           (a) a record 0 containing filename date time and size

           (b) a 1K block size option

           (c) CRC-16.


        In case of questions, please refer to ymodem.doc, part of yzmodem.zoo

        (yzmodem.arc) for for the official YMODEM protocol.


        12.2.11  Qmodem-G/Streaming XMODEM  The Qmodem program and certain

        bulletin boards provide an ACKless XMODEM mutant protocol selected

        with the Qmodem G protocol menu choice.


        The sx and rx -g commands support this mutant XMODEM.


        EXAMPLE: rx -g qmodem.fil



        12.2.12  WXMODEM (People-Link)  ZCOMM supports WXMODEM protocol

        downloads with the rw command.  On the People-Link timesharing

        service, WXMODEM downloads are faster than XMODEM downloads.

        Throughput, reliability, accuracy, and amenities are not as good as

        ZMODEM or SuperKermit, but neither of these protocols are currently

        available on that system.  WXMODEM adds up to 127 garbage bytes to

        transferred files.  Omen Technology does not recommend WXMODEM for use

        over noisy phone lines.


        EXAMPLE: rw file1



        12.2.13  MODEM7 Batch  The MODEM7 batch protocol passes CP/M file

        names from the sending program to the receiver one character at a

        time.  The compatibility, throughput, and reliability problems of this

        kluge prompted the development of YMODEM.  Nonetheless, when it

        becomes necessary to transfer files with a program lacking more

        advanced protocols, MODEM7 batch is better than nothing.


        File names transmitted with the MODEM7 batch protocol must obey the

        restrictions of both 8 bit CP/M and DOS.  The f option cannot be used

        with MODEM7 batch.  Data transfer within MODEM7 batch uses XMODEM

        protocol, and all of XMODEM's weaknesses discussed above apply to

        MODEM7 batch.  MODEM7 batch does not preserve the modification date or

        exact file contents.


        EXAMPLE: s7 file1.ext *.baz sends files with MODEM7 batch.





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        EXAMPLE: r7 receives one or more files with MODEM7 batch.



        12.2.14  Telink/FIDO  The Telink protocol expands upon the MODEM7

        batch kluge with a specially formatted block containing the length of

        the file and the local DOS time and date.  All of the MODEM7 batch

        compatibility and reliability problems apply to Telink.[4] The zmodem

        Z numeric parameter or the z file transfer option may be used to

        correct the time/date stamping of files transferred between different

        time zones.


        EXAMPLE: zmodem pZ120;  st file1.ext *.baz Sends the specified files

        with a 2 hour time zone adjustment.



        EXAMPLE: rt -z60 Receives one or more files with a 60 minute time zone

        adjustment.



        12.2.15  SEAlink  When transferring files with the CLINK 1.13

        compatible programs, ZCOMM's rb and sb commands recognize SEAlink's

        modified Telink protocol.  The rb command allows a transmitting

        SEAlink program to use sliding windows.  Telink time zone and file

        name considerations apply to SEAlink.  In addition, because SEAlink

        uses all 256 of the possible 8 bit codes for both data transfer and

        protocol management, some modems and networks that operate with XMODEM

        will not accommodate SEAlink.  As with the MODEM7 and Clink protocols

        mentioned above, the SEAlink protocol is included for convenience in

        situations where the YMODEM and ZMODEM protocols are not

        implemented.[5]


        EXAMPLE: zmodem pZ120;  sb file1.ext *.baz Sends the specified files

        to a SEAlink program with a 2 hour time zone adjustment.



        EXAMPLE: rb -z60 Receives one or more files from a SEAlink program

        with a 60 minute time zone adjustment.




        __________


         4. ZCOMM's rt and st commands were verified with Minitel 3.0 by Tom

            Jenning's Fido Software; other Programs may not produce the same

            results.


         5. ZCOMM's SEAlink was verified with CLINK 1.13 by Systems

            Enhancement Associates.  Other Programs may not produce the same

            results because of ambiguities in the SEAlink documentation and

            undocumented protocol variants.




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        12.3  Kermit


        12.3.1  ZCOMM Kermit Capabilities At a Glance

         Local operation..................Yes

         Remote operation.................Yes

         Transfers text files.............Yes

         Transfers binary files...........Yes

         Wildcard send....................Yes

         Filename collision avoidance.....Yes

         Can time out.....................Yes

         8th-bit prefixing................Yes

         8 bit serial data................Yes

         Sliding Windows..................Yes

         Long Packets.....................Yes

         Repeat count prefixing...........Yes

         Alternate block checks...........Yes

         Terminal emulation...............Multiple

         Communication settings...........Yes

         Transmit BREAK...................Yes

         IBM mainframe communication......Yes

         Transaction logging..............Yes

         Act as server....................no

         Talk to server...................Yes

         Advanced commands for servers....Yes

         Handle file attributes...........no

         Programmable reset string........Yes


        Kermit operates with a wide range of computer systems, including those

        whose restrictive terminal interfaces prevent XMODEM transfers.

        Kermit uses an encoding technique called quoting to represent control

        characters and (if necessary) parity bits with standard printable

        characters.  It is one of the few asynchronous error correcting

        protocols that work properly with half duplex IBM front ends.  Because

        of the overhead from character quoting, Kermit is less efficient

        (slower) than ZMODEM.


        Kermit can transfer one or more files per command, preserving the

        exact file length.



        EXAMPLE: kermit sb file1 file2



        EXAMPLE: kermit rb



        12.3.2  Incompatible Kermit Dialects  When sending files with the

        Kermit Protocol, ZCOMM uses all 8 bits for the transfer unless a 7 bit

        parity mode (e.g., ena -7e) is used, the kermit 7 numeric parameter is

        non zero, or the other program requests 8th bit qouting.  If ZCOMM is

        using a 7 bit parity mode (such as ena -7m), ZCOMM requests 8th bit



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        quoting unless the kermit 8 numeric parameter is non zero.


        -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

                        Both programs must use the same parity

                        for Kermit file transfers to succeed.

        -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


        Kermit does not provide an automatic means of forcing both the sender

        and receiver to use the same dialect.  Files cannot be transferred if

        the two programs disagree on parity handling, Such failures are quite

        commonplace.  A common symptom is a transfer that starts up normally

        but always fails at the same block.  Setting appropriate parity

        corrects these Kermit failures.


        ZCOMM's Kermit AutoDownload(TM) (enabled with the K mode) allows the

        term function to sense the beginning of a Kermit file download, make

        the proper determination on whether to use 8 bit serial data, and

        execute the file download without user intervention.


        12.3.3  Kermit Performance Enhancements  Super-Kermit (Kermit with

        Sliding Windows) transmits multiple packets before waiting for a

        response, increasing throughput with timesharing systems and networks.

        ZCOMM uses sliding windows and CRC error detection if the other

        machine's Kermit supports them.


        ZCOMM also supports long packets for increased throughput with

        suitable systems, including many that do not support sliding windows.

        ZCOMM allows Kermit long packets up to 1000 characters on DOS, up to

        2048 on 32 bit Unix systems.


        The maximum send packet length is set by the kermit l numeric

        parameter.  ZCOMM will ask for sliding windows if this is set to 94 or

        less.


        EXAMPLE: k pl94



        The maximum receive packet length is set by the kermit L numeric

        parameter.  ZCOMM will ask for sliding windows if this is set to 94 or

        less.


        EXAMPLE: k pL94



        With the default values for the kermit l and kermit L parameters,

        ZCOMM will choose long packets over sliding windows when a choice is

        possible.


        ZCOMM supports 12 bit Kermit checksums and 16 bit Kermit CRC for

        professional error detection performance.  ZCOMM uses the most

        reliable Kermit error correction available.  Shorter checksums may be



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        forced by changing the kermit b numeric parameter.


        12.3.4  Accessing Kermit Servers  The commands to start up a Kermit

        server vary from system to system.  Unix C-Kermit can be started in

        server mode with kermit -ix given to Unix or VMS.  When the Kermit

        server is active, the ZCOMM get, send, and remote ...  commands may be

        used.  The ZCOMM finish command causes the remote Kermit server to

        exit to its operating system.


        12.3.5  Kermit Caveats  Some versions of Kermit translate files as

        they are sent, by default!  Typical modifications include CR/LF to NL

        transformations and CPMEOF stripping.  Before transferring binary

        files, such editing must be disabled with SET FILE TYPE BINARY or

        similar commands given to the other program.  The demonstration in

        Chapter 9 includes several Kermit server access and file transfer

        commands.


        If the Kermit protocol doesn't work with IBM mainframe communications,

        incorrect ASCII/EBCDIC translate tables may be the problem.


        Some mainframe "front ends" require special characters or a break

        signal to recover from transmission errors ("line hits").  The

        kermreset string parameter (q.v.) may be programmed with the required

        sequence.


        SEE ALSO: kermreset string parameter


        When downloading files from some versions of Kermit, best results may

        sometimes be obtained by starting ZCOMM's kermit receive before typing

        the carriage return that starts the sender on the remote.  If the

        other program includes an adjustable initial delay, you can save time

        by setting it to zero.


        SEE ALSO: kermit d numeric parameter


        SEE ALSO: K mode (Kermit AutoDownload(TM))


















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        12.4  Uploading Files to Unix Systems


        Files may be uploaded to Unix systems conveniently and quickly with

        ZMODEM.  Unix flavors of Professional-YAM support the full ZMODEM-

        90(TM) feature set including Crash Recovery and selective transfers

        with the rz command, a hard link to the /usr/bin/yam program.


        The undos program may be used to remove carriage returns files

        uploaded to Unix machines.


        When accessed over a network, some systems require additional control

        characters to be escaped.  The sz command e option may be used to

        escape all control characters.


        SEE ALSO: e option


        Individual control characters can be escaped with the zmtxesc string

        parameter.


        SEE ALSO: zmtxesc string parameter


        If the Unix system is operating with 7 bits, the sender's zmodem d

        parameter may have to be increased to allow the rz program time to

        change Unix to 8 bits for the transfer.


        SEE ALSO: zmodem d numeric parameter


        Pro-YAM may not be available on a particular system.  The rz program

        supports a subset of ZCOMM's ZMODEM features.[6]




        __________


         6. If rz is not installed on the Unix system, unpack the rzsz.zoo

            file on your MSDOS system with: looz -e rzsz.zoo given from the

            DOS prompt.  On Unix systems with Professional-YAM installed, the

            rzsz source files and man pages are located in

            /usr/src/command/rzsz.  Next, the command source zupl.t calls the

            zupl.t script to upload the bootstrap file minirb.c, compile it,

            and use it to upload the remainder of the source files.


            After the rest of the files have been uploaded, compile rz.c and

            sz.c using the directions given in the README file and in the C

            source files.


            The manual "pages" rz.1 and sz.1 may be formatted with nroff

            commands such as


                    nroff -Tlp -man rz.1 sz.1




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        12.5  Downloading Files from Unix Systems


        To download files from Unix(TM) systems, use the Unix sz command to

        send the desired files to ZCOMM.  To Unix keyboard: sz file ...

        ZCOMM's ZMODEM AutoDownload(TM) takes care of the rest for you, saving

        unnecessary keystrokes.


        If one or more of the files already exists on the destination disk,

        use sz -y file ...  instead, to replace the old copies on your

        computer.


        Another useful option sends only the files that exist on both

        computers (Y), and furthermore sends only those that are newer (n):

        sz -Yn file ...


        When files are long and transmission slow, you can save time by

        squeezing them first with sq.  Source for a Unix compatible version of

        sq is available in xsq.cq.[7] The zoo program, available for DOS and

        Unix, may also be used to compress file(s) before transmission.


        Omen Technology products support ZMODEM compression with the Z option.

        All Omen Technology products support compression by Run Length

        Encoding (RLE).  Unix flavors of Professional-YAM also support LZW

        compression.


        Unix source files normally do not contain carriage returns used by

        CP/M and DOS.  Some CP/M or DOS programs, such as C compilers, do not

        require carriage returns in the source files.  Others, such as the

        Microsoft Macro Assembler, become quite confused by such files,

        although such files fully meet the requirements of the ASCII standard.


        Carriage Returns may be added before downloading with the todos or

        tocpm programs.  Carriage returns may be added during the transfer

        with the sz a option.  Carriage Returns may be added after the

        transfer by some program editors, including uEMACS.  (Other editors,

        such as DOS edlin may crash trying to edit such files.) Short files

        (less than 64kb) may be converted using ZCOMM's read and create

        commands to pass the data through ZCOMM's capture buffer.


        Text files may also be downloaded using the capture buffer if sz has

        not been installed on the Unix machine.


        If a file or set of files are to be transported between two Unix

        systems, it may be helpful to place them in a tar or cpio archive (and

        possibly squeeze the archive) before transmission.  This procedure



        __________


         7. /usr/src/cmd/xsq.c on Unix systems.




        (C) 1990 Omen Tech Inc              Chapter 12 Protocol File Transfers


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