On 6/29/20 4:37 AM, R.Wieser wrote:
> No.   It means that when A connects to B than B will do /nothing/,
> other than to wait until C connects to it   (and vise vera).

I've gathered this understanding by now.  But I don't recall where the
multi-threaded parallel highly latent discussion was when I wrote what
you replied to.

> And yes, that means that /both/ connections terminate at B.

This means that B is active in the connection on many levels.  Including
needing something to copy data between the independent connections.

> :-) I ment that in the sense of whatever kind of (physical) connection
> was used, regardles of it being ethernet, serial, "USB bridge"
> or other.

I largely agree.  But you do care /some/ amount greater than zero
because of your comments about speed.  ;-)

> :-) Mind you, I'm attempting to connect two Windows 'puters.

It doesn't really matter what the A and C devices are, much less what OS
they are running.

> But does Linux automatically grab a serial connection and feed it
> into its OS ?

Let's elide the typical serial line signaling requirements for now.

The data will come in the serial port and be available at a TTY device;
e.g. /dev/ttyS0 or /dev/ttyS1.

That data will sit in buffers until something reads it.

So, yes, data does come in and wait for something in the OS to use it.

The typical serial line signaling requirements would prevent the source
from actually sending.  But the fact that something does want to send is
made available to the OS and programs thereon.

> Or does it allow me to chose if I want to handle the raw data myself ?
> In the latter case there is zero problem.

You choose to take it from the TTY device and do what you want with it.

Aside:  Data will not flow between TTY devices on it's own.  You must
have something actively copy the data between them.

> How is that a problem ?    How could that be used to break the
> isolation between A and C ?

It most likely can't be used to break isolation.  But it is something
that the Pi needs to keep track of and deal with.

> I think your definition of "will very much be an active participant"
> is a bit different from mine.

You have been quite adamant that the Pi is passive.  And here you are
almost acknowledging that it's active.

> But why else do you think I would put it in there ?   To play
> paperweight ?

Na.  The Raspberry Pi is fairly light and doesn't make a good paperweight.

> Thats impossible.  All my decisions are of the passive kind !
> Uninformed and not even thinking about how that might be a bad idea,
> 'cause that would be something active. :-p

You have indicated that there is criteria for what is and is not passed
between A and C.  Executing that criteria is an active process.  There
is at least one logical condition in it.  Executing / walking /
performing that logic is an active process.  It is more than blind
packet in packet out behavior.

> I think you misunderstood.    I simply copied one the (text) contents
> of the clipboard from one machine to the clipboard on another machine.
> From there the other machine could do with it whatever it wanted.
> Another KISS style solution. :-)

Let's agree to disagree.



--
Grant. . . .
unix || die

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