Question about X on the arm's.

Gene Heskett gheskett at
Mon Nov 28 13:49:03 UTC 2016

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?

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 <>

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