XDMCP not working at all for GDM/XDM/etc.

[Brian Keener]

Originally posted in aolm.

XDMCP does not respond to any of my X-server's attempts to connect. This is
regardless of which dm I pick, GDM/XDM/MDKKDM/KDM

I had XDMCP working with all these methods previosly, and it mysteriously has
stopped working for ANY of them. Using Cygwin as the X-server on an XP box, a
WinME box, a Win2K Server box, and two other Mandrake boxes all have the same
result: The checkered X background appears for a moment, and then disappears
on the Cygwin clients, and on the Mandrake clients nothing ever happens.
I've set up a desktop shortcut that executes "xwin.exe -query servername" on
the Cygwin boxes, which previously worked fine. I've never tried to do this
with a Mandrake client, but as near as I can tell the command should be
"X -query servername :1" or something similar. At least, this launches a new
X-server on screen :1, but nothing ever happens.

Also, I say nothing ever happens, but that's not quite right. OCCASIONALLY,
I'll be working on the server (service dm restart, telinit 3, telinit 5, gdm,
other commands) and I'll switch back over to the X-server and there's suddenly
a login screen. This specifically happened once last night: I rebooted,
telinit'd to runlevel 3, and then executed "gdm &" as root. I got a login
screen at that point on any connections using XDMCP, from the Windows boxes or
from the linux boxes. I rebooted, followed those steps as near as I can
recall them, and got no connection. I got a plain vanilla XDM login screen
once as well.

I've followed the instructions for XDMCP that are at
[url]http://www.tldp.org/HOWTO/XDMCP-HOWTO/[/url] to no avail. These are the instructions
that I followed to get XDMCP running in the first place.

"netstat -l | grep xdmcp" shows that xdmcp is listening correctly. There are
no firewalls on any of the machines involved.

When I reboot the target computer (servername)
sometimes the X-server running on one of my mandrake computers will report
quitting on signal 11. Also, when running KDM as the DM, sometimes I will
get an error similar to "xlib: invalid mit-magic-cookie" both on the X-server
and in kdm.log. Here's the actual error, as logged in /var/log/kdm.log.

Xlib: connection to "192.168.5.15:0.0" refused by server
Xlib: Invalid MIT-MAGIC-COOKIE-1 key

This error is reported 5 times for each attempted login in /var/log/kdm.log.
I can't seem to locate where gdm would store any applicable error messages...

SSH'ing into the boxes and running startkde or gnome-session works just great,
which is what I'm doing in the meantime...

Any ideas? What other information would be useful?

Brian K

[M. Strobel]

Brian Keener wrote:

> Originally posted in aolm.
>
> XDMCP does not respond to any of my X-server's attempts to connect. This is
> regardless of which dm I pick, GDM/XDM/MDKKDM/KDM
>
> I had XDMCP working with all these methods previosly, and it mysteriously has
> stopped working for ANY of them. Using Cygwin as the X-server on an XP box, a
> WinME box, a Win2K Server box, and two other Mandrake boxes all have the same
> result: The checkered X background appears for a moment, and then disappears
> on the Cygwin clients, and on the Mandrake clients nothing ever happens.
> I've set up a desktop shortcut that executes "xwin.exe -query servername" on
> the Cygwin boxes, which previously worked fine. I've never tried to do this
> with a Mandrake client, but as near as I can tell the command should be
> "X -query servername :1" or something similar. At least, this launches a new
> X-server on screen :1, but nothing ever happens.
>
> Also, I say nothing ever happens, but that's not quite right. OCCASIONALLY,
> I'll be working on the server (service dm restart, telinit 3, telinit 5, gdm,
> other commands) and I'll switch back over to the X-server and there's suddenly
> a login screen. This specifically happened once last night: I rebooted,
> telinit'd to runlevel 3, and then executed "gdm &" as root. I got a login
> screen at that point on any connections using XDMCP, from the Windows boxes or
> from the linux boxes. I rebooted, followed those steps as near as I can
> recall them, and got no connection. I got a plain vanilla XDM login screen
> once as well.
>
> I've followed the instructions for XDMCP that are at
> [url]http://www.tldp.org/HOWTO/XDMCP-HOWTO/[/url] to no avail. These are the instructions
> that I followed to get XDMCP running in the first place.
>
> "netstat -l | grep xdmcp" shows that xdmcp is listening correctly. There are
> no firewalls on any of the machines involved.
>
> When I reboot the target computer (servername)
> sometimes the X-server running on one of my mandrake computers will report
> quitting on signal 11. Also, when running KDM as the DM, sometimes I will
> get an error similar to "xlib: invalid mit-magic-cookie" both on the X-server
> and in kdm.log. Here's the actual error, as logged in /var/log/kdm.log.
>
> Xlib: connection to "192.168.5.15:0.0" refused by server
> Xlib: Invalid MIT-MAGIC-COOKIE-1 key
>
> This error is reported 5 times for each attempted login in /var/log/kdm.log.
> I can't seem to locate where gdm would store any applicable error messages...
>
> SSH'ing into the boxes and running startkde or gnome-session works just great,
> which is what I'm doing in the meantime...
>
> Any ideas? What other information would be useful?
>
> Brian K

Sounds confused and confusing. Be more concise next time, like what do
you want on the mandrake boxes (login to serverbox? Chooser?)

SSH sets up its own xauth, so this seems to be the problem.

Try a ssh to your serverbox without the -X option, then set the display
variable to your clientbox (export DISPLAY=192.168.xx.xx:0.0) and start
an X program like xcalc. This would verify the access problem.

And try to trace the network, some sniffers like ethereal (ethereal.com)
decode the packets quite well.

Then be aware that some configuration files like Xservers and Xaccess
are duplicated througout your directory tree. Just keep them ALL in sync.

Max

[Brian Keener]

In article <bkftim$bjn$1@online.de>, M. Strobel wrote:

> Brian Keener wrote:

>> Originally posted in aolm.
>>
>> XDMCP does not respond to any of my X-server's attempts to connect. This is
>> regardless of which dm I pick, GDM/XDM/MDKKDM/KDM
>>
>> I had XDMCP working with all these methods previosly, and it mysteriously has
>> stopped working for ANY of them. Using Cygwin as the X-server on

an XP box,

>
> Sounds confused and confusing. Be more concise next time, like what do
> you want on the mandrake boxes (login to serverbox? Chooser?)
>
> SSH sets up its own xauth, so this seems to be the problem.
>
> Try a ssh to your serverbox without the -X option, then set the display
> variable to your clientbox (export DISPLAY=192.168.xx.xx:0.0) and start
> an X program like xcalc. This would verify the access problem.
>
> And try to trace the network, some sniffers like ethereal (ethereal.com)
> decode the packets quite well.
>
> Then be aware that some configuration files like Xservers and Xaccess
> are duplicated througout your directory tree. Just keep them ALL in sync.
>
> Max
>

Sorry. It made sense when I typed it. Anyway, my goal was for me to
be able to type "Xwin -query servername" in Cygwin or "X -query
servername :1" on my Mandrake desktop box and have a login prompt
appear on my remote machine's Xserver.

I resolved this problem anyway: Either it was a DNS problem which I
rectified on the linux box, or it was a problem with the contents of
the dir /var/lib/gdm. I wiped the various .Xauth and other files in
that directory, and removed the DNS entries for my old ISP from
resolv.conf, and the problem magically dissappeared. I really doubt
it was a DNS problem, but you never know. Since it was a MAGIC-COOKIE
error I imagine it was the Xauth files that did it. Or random coincidence.

Brian K