ZIP - Protocol?

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MCbx

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Aug 5, 2015, 2:02:01 PM8/5/15
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Hello
Is there any documentation for protocol and method of transfer used in ZIP program? I think about using it in my DOS machine and writing something for my modern Linux box to make it easily exchange files with old PC.
I've used ZIP since... well, at least 2005, but only in DOS-DOS and DOS-Win9x transfers.
Yours
MCbx

Eric Meyer

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Aug 5, 2015, 2:17:07 PM8/5/15
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Hi "MCbx",

Unfortunately, ZIP really only worked well with DOS and Win9x. It relied on
disabling interrupts in order to send a packet of data, and that's unlikely to
work with a more modern OS. There is no documentation of recent versions of
the protocol. I did try that once long ago with someone who wanted to develop
a ZIP client for another OS, probably Linux! But it wasn't successful.
Perhaps you'll find another utility that will work for you.

Best wishes -- Eric Meyer.

dmccunney

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Aug 5, 2015, 4:07:48 PM8/5/15
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You might want to look at Michael Brutman's mTCP package for DOS. In
includes a lightweight TCP stack for DOS, and an assortment of
utilities including an FTP server. It might be a way to get things
between DOS and Linux.

mTCP is open source, and available here:
http://freedos.sourceforge.net/software/?cat=net

(WattTCP from the same place might be another option.)

Another option might be Chuck (Omen Technology) Forsberg's rzsz, which
adds Xmodemk, Ymodem, and Zmodem transfers to DOS. You can get source
for it here: ftp://archives.thebbs.org/file_transfer_protocols/rzsz.zip,
and ports of rzsz are available for Linux.

> Yours
> MCbx
______
Dennis
https://plus.google.com/u/0/105128793974319004519

Mark P. Fishman

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Aug 5, 2015, 4:15:50 PM8/5/15
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Kermit? I believe it's still available, and runs on Linux and MS-DOS.


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dmccunney

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Aug 5, 2015, 6:34:11 PM8/5/15
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On Wed, Aug 5, 2015 at 4:15 PM, Mark P. Fishman <mfis...@alum.mit.edu> wrote:
> Kermit? I believe it's still available, and runs on Linux and MS-DOS.

IIRC, yes, and yes. But I used Kermit long ago, and while it was
available for just about everything, performance was nothing to write
home about. If the choice for me was Zmodem or Kermit, Zmodem won
handily. It used a larger default packet size, and took a "No news is
good news" approach. Protocols like Xmodem and Ymodem expected an
acknowledgement of successful receipt after each packet. Zmodem
simply sent, and didn't do anything unless the other side sent a
response that meant "That list bit was garbled. Send it again?"
IIRC, Zmodem also used CRCs to check successful transmission rather
than checksums that were vulnerable to transposition errors.
______
Dennis

MCbx

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Aug 5, 2015, 8:55:12 PM8/5/15
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Hi
Thanks for Your answer. I was thinking about reimplementation of protocol in Linux, but before my e-mail got on the list, I decided to make a small research using ZIP 2.22. I found that ZIP doesn't work between DOS in VM (both VirtualBox and DOSBox) and real machine, so I wanted to know why. I "recorded" serial ZIP communication between two PCs and started to send my own data to ZIP running in a real Win95 computer. I found the cause: Generally, ZIP requires very quick reactions on both sides, especially during "pinging back" data. Small delay, normal in multitasking OS, and there is a timeout (some timeouts just cause error, some may "loop" a server). Tight timeouts make ZIP software both fast and safe (much lower possibility of unnoticed error, if any) but requires a constant system usage, like in single-tasking DOS.
MCbx

Eric Meyer

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Aug 5, 2015, 9:02:39 PM8/5/15
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You are absolutely correct. The reason was speed, not safety; ZIP verifies
data integrity, as I would hope all such utilities do.

MCbx

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Aug 14, 2015, 12:21:24 PM8/14/15
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Hello
I have good experience with Kermit and bad with ZModem. But with Kermit before it became too bloated. Kermit is quite cross-platform - I found that Kermit from Debian 7 can talk with Kermit in Z80 CP/M machine.
ZModem is in fact much faster by design, but has fewer features and requires more work to transfer files (mostly lack of server mode requires to play with text lists, which is not good in a quick transfer).
Anyone knows an alternative working with parallel port?
MCbx
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