Category : Communication (modem) tools and utilities
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CHAPTER 16 INTRODUCTION TO FILE TRANSFER

VTERM gives you five different methods of transferring
files between your PC and another computer:

þ Text (Protocol-Free) Transfer
þ XMODEM
þ VTRANS7
þ VTRANS8
þ Kermit

These file transfer methods are called protocols. Each
one has advantages that make it preferable under certain
circumstances. The XFR files included on this diskette
explain the protocols and give instructions for using them.


WHICH PROTOCOL SHOULD YOU USE?

VTERM/220 supports five different file transfer methods.
Which should you use?

When we wish to transfer files at Coefficient Systems, we
use the protocols in this order of preference:

1. VTRANS8
2. Kermit
3. VTRANS7
4. XMODEM
5. ASCII Text

The main determining factor is which protocol is supported
on the host computer. When more than one is supported,
we generally use the more highly preferred protocol.

Our proprietary protocol, VTRANS8, is the fastest, most
reliable, and easiest to use. If your host computer is a VAX
under VMS, a PDP-11 under RSTS/E, or a UNIX/XENIX system, this
should be your first choice. (Your VTERM package includes fully
operational host software in source format for those operating
systems -- see VTRANS.XFR.)

However, VTRANS8 offers no simple way to send a group of
files conveniently. (You have to write a command file on the
host to do so). Kermit, in contrast, allows you to conveniently
send a group of files with a wildcard command. If you want to
send a whole group of files at once, therefore, you might choose
Kermit over VTRANS8.

Moreover, even if you have one of the host systems for
which we supply VTRANS software, you may not be able to use
VTRANS8. You may not have the necessary compiler on your system.
Or your installation may use networks, multiplexers or other
communication devices that make it impossible for VTRANS8 to
work.

VTRANS8 depends on being able to transmit all 8-bit
characters back and forth between the PC and the host. That's

what makes it so fast. But this means that all devices between
the PC and the host must be able to pass 8-bit characters through
to the next device. Unfortunately, many devices treat certain 8-
bit characters as special commands that they interpret -- and act
on -- instead of sending them through to the intended recipient.

If you can't use VTRANS8, see if there is a version of
Kermit available for your host system. Included with this manual
is a list of Kermit implementations currently available from
Columbia University.

Kermit is generally slower than VTRANS8 but equally reliable if
the host software is properly written. Its support of wildcard
file transfer makes it the most convenient protocol for sending
groups of files at one time.

VTRANS7, another proprietary protocol of Coefficient
Systems, is supported for VAX computers running the VMS operating
system, for UNIX/XENIX systems, and for PDP-11's under RSTS/E and
RSX11-M/M+.

It's equal to VTRANS8 in error detection, reliability, and ease of
use. Moreover, unlike VTRANS8, VTRANS7 is compatible with virtually
all communications equipment. However, VTRANS7 is slower than both
VTRANS8 and Kermit.

As a last resort for binary file transfer, the public
domain protocol XMODEM is available for a small group of host
computers as well as a larger variety of micros. It's also
available on most bulletin boards. VTERM supports the enhanced
version of the XMODEM protocol which permits CRC error detection.
XMODEM's drawback is that it isn't as fast or reliable as
VTRANS8, or as reliable as Kermit and VTRANS7.

ASCII Text transfer is significantly different from the
other protocols. (In fact, strictly speaking, it's not a
protocol at all. It's a way of sending files without a
protocol.)

ASCII Text transfer does not check to see whether data is
received correctly, so it is subject to errors when the
connection is noisy. The other protocols automatically resend
data that is received incorrectly. Also, ASCII Text transfer is
limited to files that contain only printable characters, so you
cannot use it to transmit .EXE files and others that contain
binary (8-bit) data.


WHAT ABOUT XON/XOFF PROTOCOL?

Some communications programs support something their
publishers call XON/XOFF Protocol. This is really just ASCII
Text transfer with XON/XOFF enabled. To do the same thing with
VTERM, set the Auto XON/XOFF option on Setup Screen One to a
value (from 64 to 512) and use ASCII Text transfer.


HOW TO TRANSFER FILES

VTERM has been designed so you can use many of the same
commands and procedures when you transfer files, regardless of
which protocol is in use. Unfortunately, the protocols differ so
greatly from each other that procedures for using them cannot be
made completely uniform. For this reason, instructions for each
protocol are given separately in the other .XFR files.

The rest of this chapter gives a brief overview of the
mechanics of transferring files with all five protocols.


Setup Screen Two

Before you send or receive a file, you may wish to bring
up Setup Screen Two with the Alt-S key to change one or more
parameters that affect file transfer.

Setup Screen Two has five pages, one for each protocol.
To display the page for the protocol you wish to use, move the
cursor to the Protocol field and press one the Plus (+) key until
the desired page appears.

The only reason you should bring up Setup Screen Two is
to check or change an option that appears below the Protocol
field. The Protocol field itself does not determine which
protocol is in use, nor does it affect file transfer in any other
way. Its only effect is to select which page of options appears
on Setup Screen Two.

When any setup screen is displayed, pressing Alt-P (for
put) causes all options on all pages of all setup screens to be
saved in the current setup file. However, options that appear in
the File Transfer Window (see below) are saved only when you
press Alt-P while the File Transfer Window is displayed.
Similarly, when any setup screen is displayed, pressing

Alt-G (for get) causes all options on all pages of all setup
screens to be restored from the current setup file. However,
options that appear in the File Transfer Window (see below) are
restored only when you press Alt-G while the File Transfer Window
is displayed.

See Part 2 of the Evaluation Kit for more information on
Setup Screen Two.


Starting File Transfer

Once the settings on Setup Screen Two are correct, you
are ready to initiate file transfer. This is done in one of
three ways, depending on the protocol you wish to use and the
kind of software on the other computer.

To use Kermit, you run the Kermit program on the other
computer and press Alt-K to start VTERM's own Kermit. You then
use one or more Kermit commands like RECEIVE or GET to begin the
transfer. See KERMIT.XFR and KERCOM.XFR for more information.

To use VTRANS7 or VTRANS8 to exchange files with a host
computer, you run the host's VTRANS program with a command like
RUN VTRANS. The host responds with a short dialog of five or six
questions regarding the direction of transfer, the filenames to
use, and so forth. See VTRANS.XFR for more information.

To use one of the VTRANS protocols to communicate with
another PC which is also running VTERM, or to use ASCII Text
transfer or XMODEM to communicate with any other computer, you
press Alt-R (for receive) or Alt-T (for transmit) to start
receiving or sending a file. As soon as you do this, the File
Transfer Window appears.

The File Transfer Window

When you press Alt-R or Alt-T to initiate file transfer
(see previous section), a small window, like the one illustrated
in Figure 16-1, appears on the Terminal Screen with fields that
are used to specify options that need to be reconsidered every
time you transfer a file--the name of the file, for instance.

_______________________________________________________
| |
| Filename: \REP\BARB.DAT |
| Protocol: VTRANS (8-BIT) |
| Remote Filename: BARB.BAK |
| If File Exists: PROMPT |
| Ctrl-Z Marks End: NO |
| Translate: OFF |
| Remove Characters: |
|_______________________________________________________|
Arrow keys select, + changes. Alt-T=Transmit,Esc=Cancel

Figure 16-1. File Transfer Window. This illustration
shows the window for transmitting files using the VTRANS8
protocol. The window for receiving files has Alt-R=Receive
on the information line in place of Alt-T=Transmit.

The Protocol field in the File Transfer Window determines
which protocol will be used for file transfer. It should not be
confused with the Protocol field on Setup Screen Two, which only
determines which options are shown on Setup Screen Two and has no
effect on file transfer.

The Translate field in the File Transfer Window
determines whether VTERM translates certain characters when you
are operating in a language other than American English. For
this evaluation you should set the field to OFF.

The meanings of the other fields in the File Transfer
Window are explained in ASCIITEXT.XFR (ASCII Text transfer),
XMODEM.XFR (XMODEM), and VTRANS.XFR (VTRANS).

To save the currently selected File Transfer Window
options in your setup file, press Alt-P (for put) while the
window is displayed on the screen. Doing this does not save the
setup screen options.

Similarly, to restore File Transfer Window options from your
setup file, press Alt-G (for get) while the window is displayed
on the screen. This does not cause the setup screen options
to be restored.


  3 Responses to “Category : Communication (modem) tools and utilities
Archive   : VTRANS.ZIP
Filename : INTRO.DOC

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