Re: Serial port redirection

Peter Astrand
2003-12-03T16:30:37Z

> Hi. I'm trying to find a generic serial port redirection solution for a
> Linux terminal server environment. I'd like a solution based on RFC2217.
> I'm particularly interested in syncing Palm Pilot PDAs.
...
> ser2net/sredird + Kermit
> ------------------------
> Kermit has built-in RFC2217 support, but it doesn't work for me:
>
> ---
> C-Kermit>set host localhost:4911
> DNS Lookup... Trying 127.0.0.1... Reverse DNS Lookup... (OK)
> localhost.localdomain connected on port 4911
> C-Kermit>set speed 2400
> localhost.localdomain:4911, 2400 bps
> C-Kermit>connect
> Connecting to host localhost.localdomain:4911
> Escape character: Ctrl-\ (ASCII 28, FS): enabled
> Type the escape character followed by C to get back,
> or followed by ? to see other options.
> ----------------------------------------------------
> ,
> Communications disconnect
> ---

Well, this was my fault: I didn't understand how Kermit worked. When using
"set carrier-watch off", things worked much better.

* BUT: When using Kermit as a RFC2217 client for transferring files with
ZMODEM, I get "Bad CRC" pretty much all the time. This happens *both* with
the sredird, ser2net and Tactical Softwares Dialout/Server for Windows.
The problem seems to go away if I transfer files without "0xff" bytes(!)
This looks like a Kermit bug to me. I'll guess I have to talk to the
Kermit folks about this.

* ser2net is totally incompatible with cyclades-serial-client. This is
because ser2net interprets RFC2217 a bit differently. sredird sends
command "101" as ack for command "1", while ser2net sends "1". RFC2217 is
not very explicit about which way is most correct. The ser2net approach
looks better to me, but the sredird one is probably more widely used
(since Cyclades terminal server uses it, for example.) Probably, RFC2217
software needs to handle both cases.

Some more test cases:

* minicom + cyclades-serial-client + sredird:
Works

* pilot-link + cyclades-serial-client + sredird:
Does not work (see my previous mail)

* pilot-link + cyclades-serial-client + Dialout/Server:
Works perfectly.

* photopc + cyclades-serial-client + sredird:
Does not work. I get "excessive retries".

* photopc + cyclades-serial-client + Dialout/Server:
Works perfectly.

So, the combination of sredird + cyclades-serial-client does not work
correctly.

Also, I tried running "Contract I.T. Communications Analyzer" on a Windows
machine. One physical port was connected to a Linux machine via a null
modem cable. This machine ran sredird. One virtual port was created with
Tactical Softwares Dialout software, connecting to sredird. Communications
Analyzer indicated 90% Byte Error Rate! Since cyclades-serial-client was
not involved in this test, I would say that it looks like sredird is doing
something wrong.

If *anyone* has any ideas of how to solve these problem, please let me
know. I'm starting to run out of time and patience...

(Which mailing list is best for this topic?)

--
Peter Åstrand www.thinlinc.com
Cendio www.cendio.se
Teknikringen 3 Phone: +46-13-21 46 00
583 30 Linköping

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