Programmer 7500/MAX_PROGRAMMERS.iso/PROGRAMS/UTILS/MOUSE/PASSCOM.ZIP/PASSCOM.DOC

Text File | 1990-04-26 | 9.5 KB | 232 lines

PASSCOM.DOC

Program  : PASSCOM.EXE

Author   : Kevin Kiley

Company  : INTERLINK TECHNOLOGIES

Address  : 1222 5th Street
           Sarasota, Fla. 34236
           [phone]

Released : 04/25/90

Terms    : Shareware. A $10 registration fee is expected if you
           use the program on a regular basis. Registration entitles
           you to phone support and free updates. Send check or
           money order to INTERLINK.

Source   : Written completely in TURBO 'C'. No ASM code at all.
           Fully commented source code is available from INTERLINK
           TECHNOLOGIES.

WHAT IS PASSCOM?

PASSCOM is a PC DOS communications utility.

The program resides in memory and will pass ALL characters received or
transmitted on either COM1 or COM2 directly to the OPPOSITE COM PORT.

I have 4 PC's. Only ONE of them has an INTERNAL MODEM and I use this
program to SHARE that internal modem with ALL of the other PC's.

I never have to decide WHICH PC should have the modem and go through
the hassle of re-installing the modem card. The modem resides
permanently on COM2 in ONE PC and I use THIS PROGRAM and an inexpensive
ABC switch box connected to COM1 to use the modem from any one of the
other 3 PC's.

The program is a VERY SMALL Terminate and Stay Resident program (TSR)
which can be installed or removed from memory at any time from either
the DOS command line or from within a DOS batch file.

Since the program is a TSR you can still do anything you want in the
foreground on the PC with the modem in it while you are using the
modem from another PC.

This program can be used to SHARE ANY SERIAL device between a number
of PC's but the MODEM SHARING is perhaps the best example.

WHAT YOU NEED TO USE PASSCOM

IBMPC or compatible, DOS 3.1 or better, 2 com ports ( COM1 and COM2 ).

STARTING PASSCOM...

PASSCOM uses a syntax similar to the DOS MODE command. You never
need to supply the 'COM1:' or 'COM2:' parameter as you would with a MODE
command since PASSCOM already knows it will be dealing with BOTH COM PORTS.
You can, however, specify the PROTOCOL to be used for a session by supplying
the right parameters on the command line. Separate parameters with SPACES,
not COMMAS!...

PASSCOM             <-- Default protocol 2400 BAUD, NO   PARITY, 8 DATA, 1 STOP
PASSCOM 1200 N 8 1  <-- Use     protocol 1200 BAUD, NO   PARITY, 8 DATA, 1 STOP
PASSCOM 1200 E 7 1  <-- Use     protocol 1200 BAUD, EVEN PARITY, 7 DATA, 1 STOP
Etc...      | | |
            | | |
          USE SPACES
          TO SEPARATE
          PARAMETERS!

PASSCOM will complain if it doesn't like a parameter and will display an
error message and a reminder on how to the protocol should be specified.

If all is OK then PASSCOM will go memory resident and give you a message
telling you that the load was successful.

NOTE: PASSCOM will use the SAME BAUD RATE for both ports! If you need
      to share a port and ( for some reason ) need to use different
      BAUD rates then contact INTERLINK TECHNOLOGIES. I have a program
      that uses BUFFERS and is much more complicated than PASSCOM but it
      will UPSHIFT or DOWNSHIFT and allow 2 devices to communicate using
      different BAUD RATES.

USING PASSCOM...

As long as PASSCOM is resident it will re-direct all COM I/O on COM1 and
COM2 to the opposite port. If you are using it to share an internal modem
then you can go to the OTHER PC and use ANY communications software like
PROCOMM or QMODEM to place phone calls and/or UPLOAD/DOWNLOAD files.

PASSCOM re-directs the communciations interrupt vectors for BOTH COM
PORTS to get the job done. You have to be careful about what you RUN
on the PC where PASSCOM is running because of this. Do NOT run any
other software that will also re-direct the communications interrupts
or PASSCOM may stop working. This includes PROCOMM, TELINK, etc.

STOPPING PASSCOM...

Just enter 'PASSCOM T' to 'TERMINATE' the program. If no other TSR's
were loaded after PASSCOM then the program will automatically remove
itself from memory. The communications interrupt vectors will be
restored to their values at the time PASSCOM was loaded and the ports
will be released.

If another TSR has been loaded on top of PASSCOM then all it can do
is SUSPEND. It will release the communciations interrupt vectors but
will NOT remove itself from memory. Use a standard TSR FLUSH setup to
remove PASSCOM if you're are forever loading other TSR's on top of it.
This will be the only way to actually REMOVE it from memory ( other than
a quck re-boot ) if there are other TSR's on top of it. This is true
for all TSR's that are asked to remove themselves from memory under such
circumstances.

NULL MODEM CABLE REQUIRED FOR ANY DEVICE CONNECTED TO HOST PC

Any device connected externally to the COM PORTS must use a NULL modem
for things to work as desired.

In my case where I'm using PASSCOM to share 1 INTERNAL MODEM on COM2...
The OTHER PC I have connected to COM1 uses a standard NULL MODEM cable
with pins 2 and 3 reversed. If you're confused about this just ask
your dealer for an RS232 NULL MODEM cable or go to RADIO SHACK and buy
one of their 'NULL MODEM ADAPTERS' and attach it to your 'STRAIGHT THRU'
serial cable at the point where it enters the HOST PC.

If the device you're SHARING happens to be external as well ( external
modem? ) then you may or may NOT need a NULL MODEM. You don't have
to do anything different for PASSCOM. If you can use it already on
COM1 or COM2 without PASSCOM then everything should be fine.

LIMITATION: HARDWARE SIGNALS ARE NOT PASSED!

Since PASSCOM is a bit of fakery there are a few things to keep in mind
about how it works with regard to HARDWARE SIGNALS. PASSCOM will re-direct
all TRANSMIT and RECEIVE DATA that arrives on pins 2 and 3 but it will
NOT PASS HARDWARE SIGNALS! This has never caused a problem for me since
I simply use it to share an INTERNAL SMARTMODEM but there's no telling
what someone might need it for so I felt obliged to mention this limitation.

If you run a piece of software on a PC that does NOT have the actual
device installed in it and that software is depending on the status of
certain RS232 pins to be HIGH or LOW then be aware that the pins on the
port you are communciating with will NOT go HIGH and LOW exactly the
way the pins would if the device were ACTUALLY connected to it.

DTR will always go HIGH and LOW on all ports since this is controllable
from PASSCOM but other signals like CD, RTS or CTS may be lost.

Confusing? Here's an example...

Let's say you have a TEMPEATURE SENSING DEVICE installed in 1 PC
on COM2 and you are trying to use that device from another PC by
attaching it to COM1 and running PASSCOM on the PC with the SENSING
DEVICE installed.

Let us also say that the TEMPERATURE SENSING SOFTWARE that came with
the device has been hardcoded to wait for the CD (CARRIER DETECT) pin
to go HIGH (ON) before it will run its main menu. This would be pretty
silly but you never know what's out there...

When you run the TEMPEATURE SENSING SOFTWARE on the OTHER PC attached to
COM1 then this software may wait forever since it's looking at a pin
on a COM PORT that is NOT actually attached to the device itself.

CD may be HIGH over on the PC with the actual device ( running PASSCOM )
but the state of the CD pin is NOT PASSED ALONG to the other RS232
connector. Only DTR and DATA are passed on a regular basis.

Don't despair! It would be unusual if problems like these could not
be solved with the right cable. Example: In the case above... STRAPPING
pin DTR to pin CD on the PC running the TEMPERATURE SENSING SOFTWARE would
succeed in fooling it and the MENU would appear normally. STRAPPING
pins to fool software is performed at even the highest levels of DP and
it is not difficult to do.

Consult your dealer or call me if you have an unusual piece of hardware
or software that you would like to use with PASSCOM.

Most hardware signals are controllable from software and if worst comes
to worst then either you or I can alter the source code to provide
the special signals that your device is looking for ( if DOS allows access
to the pin on the UART chip! ).

OTHER PUBLIC DOMAIN PROGRAMS BY INTERLINK TECHNOLOGIES...

1. ELSEWARE v2.2 - FREEWARE - TSR REMOTE ACCESS SOFTWARE

COMPUSERVE listing  : ELSEWA.ZIP
COMPUSERVE forum    : IBM COMMUNICATIONS ( GO IBMCOM )
COMPUSERVE library  : Communications programs

ELSEWARE is a FREEWARE REMOTE ACCESS PROGRAM that allows you to use
a remote PC as if you were sitting in front of it. It works the same
(if not better) than most of the commercial software you can buy but
it requires only 8K for the HOST TSR EXE file on the HOST PC. Some video
buffers are created dynamically and the total memory footprint is
no more than 16-17K. No commercial remote access software even comes
close to this small footprint.

The REMOTE session is a full TSR POP-UP session which will NOT TAKE OVER
the REMOTE PC used to call the HOST as most commercial software will.
Password security access is included.

Easy to use SETUP SCREENS with full HELP.

Full XMODEM file transfer and AUTOMATIC FILE TRANSFER are available
for ELSEWARE as well as a unique HOST MODEM SHARING option not offered
by any commercial software.

Many CUSTOMS versions of ELSEWARE have been written to solve specific
problems out in the field. These special versions can be supplied
QUICKLY by contacting INTERLINK TECHNOLOGIES at [phone].