Question about X on the arm's.

Gene Heskett gheskett at shentel.net
Mon Nov 28 16:15:52 UTC 2016


On Monday 28 November 2016 08:49:03 Gene Heskett wrote:

> On Monday 28 November 2016 07:31:07 Thomas L├╝bking wrote:
> > On Sun, Nov 27, 2016 at 07:29:14PM -0500, Gene Heskett wrote:
> > >Okay anyone, I've had 3 or 4 folks over the last 36 hours claim
> > > that X is its own forwarding agent, why am I even using ssh?
> > > saying I'm not needing ssh at all.
> >
> > pass it "-listen tcp", it should open a connection on port 6000+n
> > (where n is the server, starting with 0) and you can "export
> > DISPLAY=remotedomain:0.0" to run X11 clients on that server.
> >
> > Notice that this is no good idea unless on a local, friendly
> > network.
>
> It is, I am the only user, and its all behind dd-wrt, which has not
> been penetrated in over a decade. If it wasn't for the need of a
> switch that allows these machines access to the net for updates and
> such, this particular cable could be 10" long. But since there is a
> gigabit switch on the other side of the room, the cat6's will be 50'
> each by the time they are fastened down with romex staples.
>
> The source SBC, an R-Pi 3b which is running an up to date raspian
> (debian Jessie built for arm) is running LinuxCNC, which is commanding
> a 1500 lb 11x36 Sheldon lathe about 65 yo, will be feeding the display
> data to a odroid64, which is claimed to be able to drive a 4k display
> with a 60 Hz refresh rate.  But when doing so over the ssh xforwarding
> encrypted path, is so slow the screen refresh is about 3x a second.
> Very distracting, and potentially dangerous when the machine can move
> 2 or 3 inches in that time frame.  Changing ssh to a faster protocol
> only got it up to 5 or 6 frames. I need to get that flicker rate up to
> a less distracting rate, something above 20 Hz if possible.  The raspi
> looks at the  machine and takes corrective action every millisecond
> but it hasn't got the memory to do the x at the same time. The
> odroid64 has 2x the memory and more gpu's and if I can get the data to
> it, ought to be ble to do it in real time.
>
> > Also, all caveats with "modern" toolkits apply here the same (they
> > tend to be dead slow over tcp because of the massive image putting,
> > you'll only get indirect GL etcetc.)
> >
> > Cheers,
> > Thomas
>
> We will see, if I can make it work. I was told I was supposed to just
> remove the '-nolisten tcp' from its launch of
> exec /usr/bin/X "$@"
> in xinit/xserverrc, and that would enable it, no one else has said to
> just remove the "no".
>
> What would be the nmap line to show that it is indeed listening?

Well, that didn't get me a listener according to an nmap scan of the 
odroid server from this machine, after I was logged into the 
odroid "server" and x was running.

The Xorg.0.log contains zero info about 'listen' directives. No mention 
at all.
gene at odroid64:/var/log$ grep listen Xorg.0.log
gene at odroid64:/var/log$ 

Where else do I need check and adjust to "enable" this listen function?

Thank you Thomas.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>


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