From:	Mitchell Spector <spector AT EnchantedLearning DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	DJGPP, interprocess communication, and DPMI
Date:	Wed, 17 Sep 1997 07:42:39 -0700
Organization:	Enchanted Learning Software
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Message-ID:	<341FEC5F.77F2@EnchantedLearning.com>
Reply-To:	spector AT EnchantedLearning DOT com
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Can a DJGPP program running in a DOS box under Windows 95
communicate with another currently-running program (either
another DJGPP program in a different DOS box or a regular
Win32 app)?

This could probably be done by reading and writing a shared file,
but that sounds awkward and slow.

To do this right, some variables would need to be shared by the
two programs.  Is there some way of telling DPMI to map a portion
of each process's virtual memory space to the same physical memory?
Or does a DOS box just not have this capability, since it's running
in a Windows 95 virtual machine?  (From the experimentation I've
done, Windows 95 seems to be careful to isolate processes in different
DOS boxes from one another, so that they don't share video screens,
for example.  So you don't seem to be able to pick an absolute
address, say a buffer in conventional memory, and just tell DPMI
in both processes to map to that physical memory.  Windows 95
tries to make sure that the two processes see different memory
there.  Maybe there's some way around this that I'm unaware of,
though.)

Thanks,

Mitchell
--
Mitchell Spector, Enchanted Learning Software
E-mail: spector AT EnchantedLearning DOT com
Visit our award-winning children's web site at:
http://www.EnchantedLearning.com

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