Power Programmierung/Power-Programmierung (Tewi)(1994).iso/magazine/msysjour/vol06/01/kermit/wnkerm.doc

Text File | 1990-12-31 | 13KB | 310 lines

            KERMIT IN WINDOWS

             William S. Hall
             3665 Benton Street, #66
              Santa Clara, CA 95051


              Introduction

     The following explains how to use the Kermit features
provided to a Windows terminal emulator by the WNKERM.LIB module.

     The Kermit protocol was originally developed by the Center
for Computing Activities at Columbia University.  Kermit provides
a way to effect an error-free file transfer files between two,
possibly very different computers provided each is capable of
running Kermit.

     If you are a regular user of Windows, then there are several
advantages to using a version of Kermit directly from Windows.
First, since Windows is multitasking, you can run simultaneous
transfers from all available communications ports (but, see the
warnings below) and continue to use other applications.
Additionally, transfers continue even when the window is iconic.

     This version of Windows Kermit can send and receive text and
binary files over seven- and eight-bit wide data paths while
using run-length encoding to achieve file compression.  One-,
two-, and three-byte CRC checksums can be selected.  A number of
packet and protocol parameters can be set by the user, and
wild-card file names can be used to send or receive a group of
files.  At any time, the transfer can be aborted in one of four
ways.

     The program currently has no remote or server features and
does not have sliding windows nor long packets.  Also, there is
no turnaround character mechanism, so certain IBM mainframe
Kermits may not work with this implementation.

     There are currently no DOS services allowing you to change
directory, display a directory, type a file, etc.  However, you
can easily use the MSDOS.EXE window or the File Manager to show
the files in a given directory.  And, you can take advantage of
some features in the SEND dialog box to help you move to another
directory and to list the files there.  After you are done, just
push the CANCEL button.  For information on using SEND, see
below.

               Basic Usage

     Kermit is very easy to use.  To send a file from the local
computer (usually the controlling microcomputer) to the remote
(host) machine the steps are:

    1.  Run Kermit on the host and choose 'receive'

    2.  Choose the 'send' option on the local machine, select
the files, and confirm the selection.  The transfer will begin
and continue until all files selected have arrived at the host or
the transfer is canceled.

     To receive a file:

    1.  Run Kermit on the host and give the 'send' command
along with the target file names.

    2.  Select 'receive' on the local machine.  The files
will continue to arrive until the transfer is complete or is
canceled.

     If verbose mode has been selected, statistics about the
transfer are displayed.  At the end of the transaction, a dialog
box appears announcing success or failure.  The display may be
obscured by the box, but it can always be moved out of the way.
However, once 'OK' has been pressed, the terminal display window
is restored and the transfer information is lost.

     Once a file transfer has begun, you can minimize the window
and have the transfer continue 'in the background'.  The icon
will display the current packet count, rolling over every
10000 packets.


                Warnings

     File transfers usually fail because of differences between
the local and remote parity and word size.  If you cannot get
even the first packet across, then try changing these parameters.

     Windows is multitasking and you can run several instances of
the same program.  If you are running more than one instance of a
terminal emulator using Kermit, watch out for possible file
conflicts such as trying to transfer files to the SAME file from
two different remote Kermits.  The DOS file system does not
always protect you from this kind of error.  It can happen that
while you are receiving a file from one source, the same file can
be successfully opened for sending.  It usually means disaster
for the incoming file.

     Similarly, if the target file is a floppy disk, do not
remove the disk until the transfer has completed.


               The Kermit Commands

     All commands for Kermit are on the 'Kermit' menu.  They are
given below along with their corresponding accelerator
keystrokes.  Commands having dialog boxes are explained in more
detail in subsequent paragraphs.

     Before a transfer begins, you can access the following
commands:

    Receive (ALT-K-R):  If the Receive menu item is chosen,
then the program enters a state where it is awaiting the arrival
of one or more files from the remote host.

    Send...(ALT-K-S):  Displays a dialog box from which
one or more files can be selected and sent to the remote host.

    Set Protocol...(ALT-K-P):  Displays a dialog box in
which the user can set various protocol parameters.

    Set Packets...(ALT-K-K):  Displays a dialog box in which
the user can set parameters for incoming and outgoing packets.

     After a file transfer begins, you can cancel the
operation in any of four ways:

    Cancel file (ALT-K-F):  Signals the remote Kermit to
discard the file currently being transferred.  The session
continues with the next file in the batch, if any.  Note that if
you have elected to keep partial files, then the current file
will NOT be deleted if you are receiving.

    Cancel batch (ALT-K-B):  Signals the remote Kermit to
terminate the session.  Only the current and the files remaining
to be transferred are affected.  The comment about partial files
in the paragraph above also applies.

    Cancel nicely (ALT-K-N): Terminates the session with an
error packet to the remote Kermit.  Incomplete files are
discarded (or saved, if the partial file flag is set).  Use this
method to cleanly terminate a transaction once the exchange has
started.

    Cancel abruptly (ALT-K-A):  Terminates the session with
no signal to the remote Kermit.  This selection is most useful as
a way to cancel a transaction before any exchange of packets has
begun.  Note that the remote Kermit will attempt to continue if
it has already started and you will may have to use other means
to terminate the remote program or you can simply let it time
out.

     Following is some detail on the commands having dialog
boxes.


              The Send Files Dialog

     When Send is selected, a dialog box with several controls
appears.  Two are list boxes; the one on the left contains all
files matching the search specification shown in the edit box at
the top; this list box functions in Extended Selection mode.  The
right list box contains a list of paths and disk drives which can
be accessed.  The push buttons allow you to select a list of
files based on the search specification, send the selected files,
or cancel the operation.

     The basic principle is:  a file name must be highlighted in
the list box to be sent.  You may send several files.  However,
you may select only those files from the current directory.
Hence files from more than one directory cannot be sent during
one transaction.

     A file can be selected in several ways.  The usual method is
to click on the name with the mouse.  More than one file can be
highlighted by holding down the control key during selection.
You can also deselect one of several highlighted items in the
list by again depressing the control key and clicking on the
item.  If you do not hold down the control key, all items will be
deselected except the one to which the mouse is pointing.

     To select a range of files, select the first one, then move
to the second one and click on it while holding down the shift
key.  You can also use the arrow keys together with the shift key
to highlight contiguous items in the list.

     If you do not have a mouse, then selection is made easier by
switching the list box into Multiple Selection mode.  Use Shift
F8 to toggle between the two modes.

     The default search specification is "*.*".  You can choose
another string to limit the files displayed in the list box.  For
example, if you tab to the edit box (or point to it with the
mouse), type "*.txt", and press the RETURN key or the SELECT
push-button.  Not only will all files having that extension be
displayed, but they will be selected as well.  You can then send
the entire list by activating the SEND button.

     At any time, you can deselect all files but one in the list
box by simply pointing and clicking on that file.  You can
deselect all files in the box by deleting the contents of the
edit box and pressing RETURN.

     You can move to another drive or directory by typing it into
the edit box and pressing RETURN or double-clicking on the
corresponding item in the directory list box.  The current search
specification is appended to the path, the program moves to the
new directory, and all matching files are displayed.  A second
RETURN or a push of the SELECT button then highlights the files
list.

     Finally, at any time, a single file located anywhere in the
system can be selected and sent.  Simply type its name, along
with any required drive and/or path information, and hit RETURN.
If the file can be found, then a switch is made to that directory
and the file name is displayed and selected.  If the file cannot
be found,  no action takes place.

     You may cancel the operation at any time by pressing the
CANCEL button.  Pushing SEND with no files highlighted has the
same effect.


              The Set Protocol Menu

     Currently you may select the following items:

    Timer (ALT-T):  If this item is checked, then after a
certain number of seconds have elapsed with no packets received,
a retry will be attempted.  If the number of retries exceed a
given threshold, then the protocol exits.  The elapsed time and
the number of retries can be set.

    Warning bell (ALT-W):  If checked, the bell sounds when a
transaction is complete or canceled.

    Verbose Mode (ALT-V):  If checked, statistics of the
transfer are shown in a modeless dialog box.  This box also has a
Cancel button which will generate a dialog box having the same
cancel options as the Kermit menu.

    Discard partial file (ALT-P):  If checked, then any file
being received in which the protocol has been interrupted by an
error condition or by the user will be deleted.

    Duplicate file warning (ALT-D):  If checked, then an
incoming file with the same name as an existing one will be
renamed so as not to overwrite the old one.  The new name appends
or replaces part of the old name with a unique generation number.

    1-Byte Checksum (ALT-1):  Selects the standard Kermit
1-byte checksum computation.  This has proved to be quite robust
in practice.

    2-Byte Checksum (ALT-2):  Selects the standard Kermit
2-byte checksum computation.

    3-Byte CRC Checksum (ALT-3):  Selects a cyclic redundancy
checksum computation.  This is most useful when transferring long
packets or when operating on noisy lines.

    Send delay for first packet:  Sets the elapsed time in
seconds before the first packet is sent when sending a file.  It
is mainly used to give the receiver time to get ready before the
initialization packet arrives.

    Retry limit:  Sets the number of retries in reading a
packet before the protocol gives up.

    Save setting (ALT-S):  If this box is checked, then
win.ini will be modified to reflect the new defaults under
[Kermit].

             The Set Packets Dialog

     Inbound and outbound packets have a number of parameters
which can be altered for varying circumstances.  You may set the
following for each type.  Note that you may also have to set the
corresponding values on the remote Kermit as well for
communications to take place.

    Start of packet:  The character which is used to mark the
start of a Kermit packet.  The default is SOH (CTRL-A).  You
would change this character if the remote machine intercepts SOH.

    Timeout:  The number of seconds that the remote Kermit
should wait before timing out.  The default is 5 seconds.

    Padding count:  The number of padding characters to send
before a packet.  The default is 0.

    Padding character:  The character to use for padding. The
default is NUL (CTRL-@).

    End of line character:  The character which terminates a
packet.  The default is a carriage return (CTRL-M).

    Quote character:  The character used to signal that the
next character is in the range 0 - 31, 128 - 159, or is a delete
character (127).  The default is '#'.

    Packet size:  The maximum length of a packet in bytes
from the sequence number byte and including the checksum
characters.  The default is 94.

     If you check Save Settings (ALT-S), then the new values will
be written to win.ini under the heading [Kermit].