Unable to connect to remote X server using X -query

[Christian Walther]

Hi there,

I'm on

$ uname -a
FreeBSD pixie.alashan.dyndns.org 6.1-RELEASE-p10 FreeBSD
6.1-RELEASE-p10 #1: Thu Nov 16 17:15:03 CET 2006
root at pixie.alashan.dyndns.org:/usr/obj/usr/src/sys/PIXIE  i386

running

$ pkg_info|grep ^xorg-server
xorg-server-6.9.0_5 X.Org X server and related programs

I set up two of my machines in my network to allow remote logins  via
xdm and gdm. Both are Linux machines, one is a current Ubuntu release
running gdm, the other one a decent Debian/testing running xdm. I'd
like to connect to both machines using the command

$ X -query <ip> -fp tcp/<ip>:7100

The X-Server starts, but it justs sits there, displaying the default
background. After a certain period of time the server is restarted,
without any error message on the console or in /var/log/Xorg.0.log
I checked the xdm/gdm configuration a couple of times, but I can use
any other none FreeBSD-host in my network to successfully connect to
the Display Manager on both machines. I even checked this with a
NetBSD machine.
I browsed through the manual and the FAQs, but I didn't find any
section that gave me a clue of what is going on. There is no Firewall
configured on my FreeBSD machine, and there is no security level set:

# sysctl -h kern.securelevel
kern.securelevel: -1

X runs just fine when being executed locally, either via startx or via
/etc/ttys using xdm.

Did I miss something?

Regards
Christian