Dec 272017
A very good description on use of ProComm's host mode.
File PROHOSTX.ZIP from The Programmer’s Corner in
Category Communications
A very good description on use of ProComm’s host mode.
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PROHOST.TXT 4864 2274 deflated

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Contents of the PROHOST.TXT file

Bulletin #13 -- April 19, 1986 -- Host Mode Problems

In an attempt to dispel some of the confusion regarding the operation
of Host Mode, this bulletin was prepared. Please note that despite
some messages to the contrary, no actual "bugs", i.e. errors in code
have been found. There are a number of considerations which need to be
correctly setup, and there appear to be some machine or operating
system incompatibilities. Not to say that there are no bugs, just no
real one verified as of yet.


The host mode depends quite a bit on the correct installation of your
modem. As there are a ton of modems out there, not all of which we are
familiar with, you may have to do a bit a reading in your modem manual.

First off, carrier detect on your modem MUST be set to follow the true
state of carrier. Carrier detect MUST NOT be forced true, or high, by
dip switch settings. Carrier detect also should NOT be set to follow
DTR. It should be set to follow the real state, or the RS-232
conventions or however your manual says it. On a Hayes modem this
means switch 6 in the UP position.

Next, data terminal ready (DTR) should also follow the true state. It
should NOT be forced high. On a Hayes modem, this means switch 1 is

Now, your cable might also have an impact on correct operation. Be
sure that the carrier detect (CD) and data terminal ready (DTR) leads
are present and in the correct configuration. Your modem manual should
have an explanation of proper cable configurations.


I know many of you have no idea what the CONFIG.SYS file is. Well, its
about time you learned. The CONFIG.SYS file is a file whose contents
control (to some extent) the configuration of your machine at boot up.
See your DOS manual for more details. The statement in the CONFIG.SYS
file that we are concerned with is the FILES= statement. This
statement controls the default number of file handles available on your
machine. The default is 8; for ProComm we recommend 20 or higher (I
use 20). Each additional handle over 8 takes an additional 39 bytes of
RAM, a small price to pay. To set this statement, create (or edit) a
CONFIG.SYS file in the same place as the command processor
(COMMAND.COM) that you boot with. Include in that file a line that


where x is 20 or greater. This file, containing this statement, MUST
be present when you boot. It has no effect otherwise. Upping this
number can also alleviate other problems indicated by "CAN'T OPEN FILE"
messages or the like.


OK, to continue... like the manual says, you need to setup all the HOST
SETUP options correctly for your modem. This is adequately covered in
the manual and I won't repeat it here. The most important of those
options is the AUTO ANSWER STRING. You can find the correct auto
answer string by checking your modem manual.

Now the most important thing: the CD MASK. This is the value we use to
mask the modem status register in order to determine if CARRIER DETECT
(or an equivalent) is present. For those purists among you, we know
that this is not a technically accurate name, but it suffices. The CD
MASK also controls the HANGUP (ALT-H) function. The most common values
are 128, 32, 64 and 16. Usually 128 or 32 will do it. Don't bother
trying all 255 possible values, stick to powers of 2. You may have to
try a couple before you get the correct one.


Ok, that should take care of most peoples problems. The parts of Host
Mode giving the most problems are the F)iles and S)hell commands. In
these cases what are doing is basically a CTTY COMx command. This
means we redirect all input and output to the comm port. Now, at this
point DOS is in charge, not ProComm, and it seems to possibly have some
problems. For instance, on our Turbo PC, if we have only one comm port
installed, and are addressing it as COM2, all redirection (either from
ProComm Host or a DOS CTTY command) went to COM1! Weird, or what? We
have not yet determined whether this is a BIOS problem on that machine
or a DOS problem. Anyway, a similar thing may occur on your machine,
especially PCjrs with that weird comm port configuration. PCjr owners
will probably need to run COMSWAP, even if this was not needed before
for normal operations. The FILES statement comes into play here as
well as new handles must be opened for I/O.

Well, there you have it. I hope this helps you all to get Host Mode
running. If you have done everything mentioned in this bulletin and
still have problems, let us know. But PLEASE try all this first, as we
do not have the time to answer these questions again over and over.

Thanks, and good luck.

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