display on remote X server

English Network/Internet
#1

Hi.
I have just upgraded to Leap, and have the following problem:
At work we run both windows and linux,
in house software is written in linux ( C with Xforms - can we have the xforms-devel package back?).
We need to run the linux programs on the windows machine (via Xming or VcXsrv)
for this to work the suse machine needs to run X with “-listen tcp”
in the past this has been problematic, but with Leap it is extremely difficult as none of the display managers seem to parse
DISPLAYMANAGER_XSERVER_TCP_PORT_6000_OPEN=“yes”
in /etc/sysconfig/displaymanager
I have tried sddm, gdm, xdm before getting kdm to work with the extra line in /etc/sysconfig/displaymanager:
DISPLAYMANAGER_KDM_LOCALARGS=" -listen tcp "
why is this so difficult? how can I get the “-listen tcp” for the other display managers?
network wise the linux machines all have a second network card with the static address 192.168.2.x
the windows machines only have access to the 192.168.2.x subnet

Derek.

#2

Are you possibly looking for the XForms Toolkit (“Forms Library for X”)? -->> Pointed to by the Fedora “xforms-devel” package.
If so, there is a package in the openSUSE repositories named “xforms” <https://software.opensuse.org/package/xforms> (“hamradio” repository)

The Xserver man page only mentions a “-nolisten trans-type” option – it seems that, it’s only possible to disable the transport type.

Assuming that, the Display Manager supports the Xorg access via TCP/IP port 6000.

  • Are you absolutely certain that the TCP/IP port 6000 is open?

(There may be either a Leap 42.1 policy or, a firewall setting, which is blocking this port.)

  • SDDM is possibly a bad choice for anything related to remote access.
  • GDM needs a security setting to be configured to not
    disable access via TCP/IP (and presumably port 6000). - XDM: no idea but, possibly the same.
  • KDM: seems to prefer XDCMP (UDP/IP).

You seem to have overlooked an alternative which may be preferable for Leap 42.1: LightDM.
[HR][/HR]The openSUSE Reference Manual is only mentioning “Remote Access with VNC”: <https://doc.opensuse.org/documentation/leap/reference/html/book.opensuse.reference/cha.vnc.html>
The openSUSE documentation set is available from here: <https://doc.opensuse.org/> and, the Reference Manual is available from here: <https://doc.opensuse.org/documentation/leap/reference/html/book.opensuse.reference/index.html>

#3

What do you mean “back”? Was it available in earlier openSUSE versions?

#4

You only describe running Xserver on Windows.

Unless you have some kind of “callback” function, there should not be any need to configure the Linux client box to “listen” for an incoming connection.
For now, your newer openSUSE box shouldn’t have to do anything differently than before to connect to your Xserver app running on Windows.

If you’re running KDE though, the current default sddm does not support “remote X” so you’d have to change to something else like lightdm.

You can do this by manually editing the config file you describe, or more safely use the YAST “/etc/sysconfig editor” and select your alternative display manager from the dropdown.

YAST > System > /etc/sysconfig editor > Desktop > Display Manager > DISPLAY MANAGER

Reboot and you should be able to connect <without> configuring any kind of TCP listening unless your app is doing something unusual.

TSU
TSU

#5

I have Leap with lightdm and using DISPLAYMANAGER_REMOTE_ACCESS=yes allows remote login via XDMCP. You are probably confused - option you mention applies to X server on openSUSE, but X server you intend to work with runs on Windows, so this option is irrelevant for your case. At least that is how I interpret

We need to run the linux programs on the windows machine (via Xming or VcXsrv)
You probably want to display results of Lunux program on Windows, not run Linux program on Windows (which is not possible anyway).

May be you should describe your setup in more details, because it is unclear what you actually try to do.

#6

hi,
thanks for your replies

dcurtisfra:
i shall check the hamradio repo but xforms toolkit used to be included on the distribution cd’s, it is a very simple library for windows buttons menus etc. in C. as I avoid C++ it is a my choice for our GUI.

–The Xserver man page only mentions a “-nolisten trans-type” option – it seems that, it’s only possible to disable the transport type.

–Are you absolutely certain that the TCP/IP port 6000 is open?

the port is open.
X has a -listen tcp which I need.

arvidjaar is right, the program runs on the suse machine but the display is on a windows machine (via Xming or similar)
Once upon a time a “yes” for the “open port 6000” in /etc/sysconfig/displaymanager sorted everything, but with each new release of suse I spend more and more time on the config files until I get something like:

derek@linux-45e8:~> ps ax | grep X
751 tty7 Ss+ 17:29 /usr/bin/Xorg -br :0 vt7 -listen tcp -seat seat0 -auth /var/lib/kdm/AuthFiles/A:0-F9hYcb

To be fair to suse they always add dire warnings in the configs that it is a security risk, but on the other hand the whole point of X is that it is a networked graphical display. When I first saw X windows alongside windows windows (back in 1990, university of edinburgh library) and could cut and paste the work I had done on the unix machines in the engineering department into a word document on the library computer - I was amazed. In fact the sysadmin in engineering told me it wasn’t possible. but I digress.

sddm does seem a bad choice, but Leap installed it by default. I shall try lightdm. I usually use gdm but for some reason it won’t run on the suse machine

lspci says:
Advanced Micro Devices, Inc. [AMD/ATI] Mullins [Radeon R4/R5 Graphics]

the other thing is I am english but have settled in france. so we tend to stick to our own machines (mine with an english keyboard, the rest of the staff with french keyboards) and share files and programs through the network. Even after 15 years over here I cannot find ],{},or () on a french keyboard without losing my train of thought.

thanks again, for your replies.
Derek

#7

No, you do not need it, at least on openSUSE.

arvidjaar is right, the program runs on the suse machine but the display is on a windows machine (via Xming or similar)
Once upon a time a “yes” for the “open port 6000” in /etc/sysconfig/displaymanager sorted everything

It cannot sort anything, because X server on openSUSE is not even contacted when program displays output on X server on Windows. It is your server on Windows that needs to listen to ports on TCP and allow remote connections from client on other hosts.

#8

After thinking about this further coupled with my general understanding of software architecture (as it is) and skimming through some of the X-forms documentation,

Although IMO any kind of remote X app <should> run on the server, it’s certainly <possible> that someone could write an app that runs <client-side>.
There may even be good reason, eg

  • The client machines all have ample resources to run the app
  • The software developer just made a mistake or doesn’t know better
  • The software developer knows how to create X-forms apps and not any other language which supports a graphical interface.
  • The data being manipulated is on the client machine and the software developer either didn’t know how to, or didn’t want to send the data to the server for processing.

There may be other reasons, and if the app is written to run client-side, then an x-server must also be running on the client machine and the server may not be used for much more than serving the pieces that run on the client or may only perform <some> functionality.

Probably the biggest clue to how this app is designed (short of seeing the app in action or the code source) is how the client initiates the network connection… Post that, and we should at least get a superficial idea what kind of connections options are being requested and what kind of server-side app is running.

TSU

#9

Ummm, not quite sure how to put this, but:I took a look at this guide: <http://codingdomain.com/linux/remote/x11/> and connected to this 13.2 machine from a Leap 42.1 machine with the following settings:

/etc/sysconfig/displaymanager :: DISPLAYMANAGER_REMOTE_ACCESS=“no” ; DISPLAYMANAGER=“kdm” ; DISPLAYMANAGER_XSERVER=“Xorg” : DISPLAYMANAGER_XSERVER_TCP_PORT_6000_OPEN=“no”
/etc/ssh/sshd_config: X11Forwarding yes ; X11DisplayOffset 10 ; X11UseLocalhost yes

SSH (with the “-X -C” options) from a Leap 42.1 Terminal CLI to the 13.2 machine – it worked, like a charm: xeyes, kwrite, libreoffice all ran perfectly.
Did the same in the other direction: from 13.2 to Leap 42.1 (with SDDM) – it worked like a charm: KF5 xeyes, kwrite, libreoffice, ksysguard, kinfocenter, dolphin, showfoto, all ran perfectly on this KDE4 Plasma box.Leap 42.1 settings:

/etc/sysconfig/displaymanager :: DISPLAYMANAGER_REMOTE_ACCESS=“no” : DISPLAYMANAGER_XSERVER_TCP_PORT_6000_OPEN=“no” : DISPLAYMANAGER=“sddm”: DISPLAYMANAGER_XSERVER=“Xorg”
/etc/ssh/sshd_config: X11Forwarding yes ; X11DisplayOffset 10 ; X11UseLocalhost yes

[HR][/HR]One little imperfection: killing the SSH connection with <Ctrl-D> needed an additional <Ctrl-C> to recover the 13.2 Konsole prompt.

#10

None of listed settings has any effect on “ssh -X” from another Unix host. Do not add to confusion.

#11

Minor disagreement:

IMHO this Thread seems to be missing a point:

  • Is utopicdog
    asking about systems where only the X-Server is running on the user machines (Thin-Client - XDMCP) or; - is utopicdog
    asking about systems where the user machines are running the X-Server and all the X11 managers (“Thick-Client” - only the applications are running on the X-Client)?

[There seems to be some site/system-specific code being used and, it’s unclear as to whether the X-Server to X-Client connection is via XDMCP (Display Manager [u]not on the user machines) or the X Window System core protocol (Display Manager and the other X11 Managers on the user machines).]

[HR][/HR]One has to be careful with XDMCP – is it using UDP/IP on IP Port 177 or, TCP/IP on IP Ports 6000 to 6005? <http://www.tldp.org/HOWTO/html_single/XDMCP-HOWTO/>.

#12

Exactly this text from utopicdog has lead me to suspect that, there may be a XDMCP versus “X Window System core protocol” issue in this Tread . . .

Yes, I can commiserate here: while visiting colleagues in France and having to use their keyboards for “out-of-office e-Mails” because, I didn’t have a company laptop at that stage of the game, was an “interesting experience”!! :sarcastic:
[HR][/HR]The difference between “Association Football” (Soccer) and “Rugby Football”: “Football is a game for gentlemen which is played by hooligans and, Rugby Football is a game for hooligans which is played by gentlemen.”