XDMCP issue - no login dialog from Linux to Cygwin

[Hislop Family]

I've just installed Mandrake 9.0, and am trying to get a session from XWin 
on Win95 across my home LAN to display an XDM login prompt. My eventual 
goal is to get it working with KDM (and that doesn't work either).

No login dialog comes up. There is a login dialog on the Linux console (for 
both XDM and KDM). From the XDM debug output, it seems that there is an 
invalid key (it's using MIT-MAGIC-COOKIE-1), although it looks like I might 
be getting an incorrectly computed IP address.

Anyway, here are some details:
o  Cygwin on Win95C (sorry, I don't know how to find the Cygwin version, 
but I downloaded it this week)
o  Mandrake Linux 9.0, looks like build 2.4.19-16mdk
o  LAN is behind a Linksys router running DHCP (both above boxes are on 
DHCP) with addresses in the range 192.168.1.100-149

I've done the really obvious things, like enabled xdm listening by 
commenting out in xdm-config
!DisplayManager.requestPort:    0

Because nothing seemed to be happening, I stopped the display manager and 
restarted XDM from the (text) console with -nodaemon and -debug 1. I won't 
bore you with the whole log dump, but there are a few interesting bits. I 
waited for xdm to get to the WaitForSomething output, then started XWin, 
first using
   XWin -query MandrakeBox
then ramping up through a series of options to
   XWin :0 -ac -query MandrakeBox -fp tcp/MandrakeBox:7100 -from 192.168.1.101
None of these appeared to make much difference, except that port 7100 
doesn't seem right (doesn't get any log activity from XDM).

The first interesting bit is an xdm error: Cannot convert Internet address 
192.168.1.101 to host name.
That doesn't appear to be very fatal (I guess I'm assuming that the host 
name is cosmetic). I'm prepared to be convinced otherwise. Anyway, it 
doesn't appear to be able to pick up the name from the network like WinXX 
does, and this address certainly isn't in the DNS (I'm using my ISP DNS). 
Nor does putting the Win95 host in /etc/hosts seem to do the trick 
(although this seems a little counter-productive with DHCP).

After that XDM sends a Willing to manage, gets a Magic Cookie, accepts a 
session ID, and waits again (you guessed, I skipped a few lines there).

A few lines further down, XDM computes the display name as 0.0.0.0:0 - this 
seems unusual to me. Is it?

Then it starts the display, and after a lot of lines to do with Xresources, 
I get the following:

AUDIT: <date> <pid> X: client 4 rejected from IP 127.0.0.1 port 1043
   Auth name: MIT-MAGIC-COOKIE-1  ID: -1
Xlib: connection to "0.0.0.0:0.0" refused by server
Xlib: Invalid MIT-MAGIC-COOKIE-1 key

Similar behaviour repeats until it times out, disables the display, and 
XWin exits. Not certain that the XWin exit and the display are coincident.

I would certainly appreciate some advice on this one. It's many years since 
I had anything to do with X-terms, but you probably guessed that already.

regards - David