ZCOMM User Manual

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 31

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").

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 32

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 33

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 34

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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 35

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 36

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 37

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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 38

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 39

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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 40

(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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 41

<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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 42

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 43

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 44

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 45

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 46

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 47

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!

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 48

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.

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 49

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

Version 17.61 TurboDial 2.33 Universal Line Printer Edition

ZCOMM User Manual 50

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.

Search This Blog

Strange Texts

ZCOMM User Manual

Comments

Post a Comment

Popular posts from this blog

BOTTOM LIVE script

Fawlty Towers script for "A Touch of Class"

MENSA IQ test with answers