Re: XDMCP Problems - Possible fix, please try

[Harold L Hunt II <huntharo at msu dot edu>]

Andrew,

Andrew DeFaria wrote:
> Sorry for the delay. We were having problems with our router and general 
> networking issues - not an nice environment to test things like remote X...
>
> Well I tried that too but it didn't work. The symptoms are exactly the 
> same.
>
> For kicks I tried the following:
>
> While on sonslinux I attempted to start another X server like so:
>
> $ X -query sonslinux :1
>
> This brought me to another console (that I could get to by doing 
> Alt-Ctrl-F8 whereas my previous console is at Alt-Ctrl-F7) and started X 
> but KDM did not attach to it. Monitoring I see:

That is genius!  I never thought of forcing people to try to make a 
connection on the actual box itself.

I ran the same command on my linux box and confirmed that it does work.

I then edited (for my display manager and distribution, this will be 
different for you) /etc/kde3/kdm/kdmrc, changed the following:

[XDMCP]
Enable=true

to

[XDMCP]
Enable=false

Then I restarted kdm ('/etc/init.d/kdm restart' for my dist), and ran 'X 
-query %hostname% :1' again and waited about five minutes.  Before five 
minutes, I saw nothing: nothing special in the log files and no login 
screen on Ctrl-Alt-F8.  Then, after about five minutes, I saw that the 
/var/log/XFree86.1.log file (and the console from which I started X) 
both said:

XDM: too many retransmissions


We now know that the failure mode when XDMCP is disabled is that after a 
five minute wait you get a message about too many retransmissions, even 
if attempting to connect from the machine back to itself via '-query 
%hostname%'.  This is the same failure mode that happens with XWin.exe, 
but it eliminates lots of possible problems.

To solve your problem, you need to revisit the instructions for enabling 
XDMCP on your Linux box:

http://xfree86.cygwin.com/docs/faq/cygwin-xfree-faq.html#q-mandrake-8.1-xdmcp

Those instructions are not complete, but they are a start that should be 
able to point you in the right direction.  Confirm that you can create a 
local connection via XDMCP before attempting a remote connection with 
XWin.exe.  Please report your results to the list so that I know if you 
have fixed your problem or not.

Thanks for your help in debugging this,

Harold