Path: utzoo!attcan!utgpu!watmath!att!dptg!rutgers!njin!princeton!udel!mvac23!thomas
From: thomas@mvac23.UUCP (Thomas Lapp)
Newsgroups: comp.lang.c
Subject: Re: Question: Turbo C and communication
Message-ID: <79.UUL1.3#5131@mvac23.UUCP>
Date: 31 Aug 89 01:03:14 GMT
References: <207600035@s.cs.uiuc.edu>
Reply-To: mvac23!thomas@udel.edu
Organization: MultiVac23, Newark, DE, U.S.A.
Lines: 46

> Nf-From: s.cs.uiuc.edu!mccaugh    Aug 25 02:17:00 1989
> Responding to: thomas@mvac23.UUCP  re: Turbo-C and comm

> >However, when the program exits, it lowers DTR as part of it's cleanup (I'm 
> >talking previously hacking in BASIC).  This is no good, since the dial command 
> >goes out and before anything happens, DTR goes low killing the modem.
> 
> >Background:  I am using a terminal emulator which operates in block mode.
> >However the modem can't handle a string which ends in an XOFF rather than 
> >a carriage return.  So.... I though I would write a 'dialer' program which
> >would dial the modem, then exit and start the emulation program so that it
> >is ready by the time the modem connects.  So while going from the dialer
> >program to the emulator, DTR has to stay high (so that the modem doesn't 
> >hang up).
> 
> > The question:  Can I do this with Turbo C?  Do I have control over those
> > bits in the 'modem port' of the PC?
> 
>  The answer is definitely yes, you can do this in Turbo-C, but first, what
>  confuses me is that you say: "I thought I would write a 'dialer' program
>  which would ... then exit and start the (terminal) emulation program...";
>  then later on: "so while going from the dialer ..., DTR has to stay high",
>  but initially, you reported: "when the program exits, it lowers DTR". It
>  sounds like your own 'dialer' program is lowering the DTR upon exit to the
>  emulator...what are you doing to make this happen?

Sorry for the confusion.  The program which lowers DTR when it exits is the
BASIC hack I put together.  The BASIC interpreter lowers DTR when it exits
to the system.  

My interest is to try the same thing in Turbo C with the hope that I could
leave DTR high when I exited back to the Operating system.  So the (not-yet-
written) C program would raise DTR, send dial command to the modem, and 
exit.  In a batch 'shell' I call the Turbo-C 'dialer' program, then 
immediately call the terminal emulater so that it is in place before the
remote modem answers :-).

From what I've been hearing, I think it can be done.  But since I am new
at C programming, I think this may not be an exercise for the novice
student.  Maybe I'll try something simpler first and work up to it :-)
                         - tom

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