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Re: Serial Connection -- shielding

On 30/03/11 01:18, MAROUNI Abbass wrote:
> Le 28/03/11 10:30, Russell L. Harris a �crit :
>> to:
>> CC:
>> * Stan Hoeppner<stan@hardwarefreak.com>  [110328 06:24]:
>>> Moczik Gabor put forth on 3/28/2011 12:01 AM:
>>>> Stan Hoeppner wrote:


> I think that the discussion diverted somehow from my original question.
> My problem was  the following :
> Two identical servers Z0 & Z1 and a null modem cable. ttyS0 on Z0
> connected to ttyS1 on Z1.
> on ttyS0 on Z0 I have a getty listening for incoming connections.
> on ttyS1 on Z1 I launch a minicom toward ttyS0 on Z0 and I login normally.
> Now When I try to do the inverse :
> Kill getty on ttyS0 on Z0 and remove it from inittab. Set getty to
> listen to ttyS1 on Z1. Launch minicom on ttyS0 on Z0 toward ttyS1 on Z1.
> I can't login all I see is garbage. All the serial parameters are the
> same on both sides.

Which are?

> I thought that logically this setup have to work since I am using the
> same setup just changing which port on which server.

Logically yes, *if* you covered the other half of the possible
combinations - it is unclear from my interpretation of your post. (I can
only 'assume' you can remove it from inittab)

> I am trying to do this for a Datacenter with hundreds of servers. This
> way I can connect two servers together with just one serial cable.
> Does it have something to do with the ttyS0 port? is it a software problem?

It could be both - or either, with out knowing the server setup, chipset
details etc and security policies I can only guess.

> Do you have any ideas ? (Apart from theoretical discussions about all
> the standards)

When I have previously encountered the situation you describe it was on
systems using hardware control, and solved by using software control.
I suggest you make sure you are using software control on *both* ends.

Ensure you are not using -h when setting up the getty session (no
hardware control)
When starting the minicom session are you using software control? Check
the global conf file, somewhere in /etc usually.

Are the chipsets identical on both servers? There are/were some
problematic serial chipsets.
Perhaps if you post the exact commands you are using to start your getty
sessions, your minicom global config, and what commands you are entering
into minicom it might be easier to diagnose.

Output of setserial from both machines might also be instructive.


Tuttle? His name's Buttle.
There must be some mistake.
Mistake? [Chuckles]
We don't make mistakes.

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