Problems w/ mgdiff across my LAN

[William A. Mahaffey III]

I am trying to use mgdiff (from ports) to look for differences between 2 
ASCII files (ANSI C, actually). I am logged into the box where the files 
reside from this box, running FreeBSD 9.3R, patched up:

[wam at kabini1, ~, 9:40:46am] 488 % uname -a
FreeBSD kabini1.local 9.3-RELEASE-p33 FreeBSD 9.3-RELEASE-p33 #0: Wed 
Jan 13 17:55:39 UTC 2016 
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
[wam at kabini1, ~, 9:40:47am] 488 %

On the other box (also FBSD 9.3R, I get:

[wam at devbox, Vector, 9:36:54am] 734 % xdiff main.c  Main.c
Error: Can't open display: localhost:11.0
[wam at devbox, Vector, 9:37:04am] 735 % which xdiff
xdiff:   aliased to mgdiff -args -wB
[wam at devbox, Vector, 9:37:17am] 736 % uname -a
FreeBSD devbox 9.3-RELEASE-p33 FreeBSD 9.3-RELEASE-p33 #0: Wed Jan 13 
17:55:39 UTC 2016 
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
[wam at devbox, Vector, 9:37:27am] 737 %

I ssh-ed into the other box (devbox) from this box (kabini1) under tcsh 
in an rxvt shell. I have been having variations of this problem for a 
while, but worked around it by cd-ing to the remote dir from this box & 
then mgdiff-ing. I can do that here as well, but that is clumsy & I 
suspect that there is a simple bit of pilot error causing this issue, 
which I would like to fix :-). Any clues appreciated. TIA & have a good one.


-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.