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From: gtan@Encore.COM (Greer H. Tan)
Newsgroups: comp.windows.x
Subject: Re: Need help debugging CAN'T OPEN DISPLAY msg
Message-ID: <13906@encore.Encore.COM>
Date: 24 Jan 91 15:55:58 GMT
References: <19965@unix.SRI.COM>
Reply-To: gtan@encore.Com (Greer H. Tan)
Organization: Encore Computer Corp.
Lines: 31

In article <19965@unix.SRI.COM> ric@ace.sri.com writes:
>I have been using a few Tektronix XP27 X terminals lately.  It is
>not uncommon to see a message like, "Cannot open display", even though
>I am certain the DISPLAY variable and other syntax and parameters 
>are properly set.  For example, the command line:
>
>	rsh myhost xeyes -display myxterm:0.0
>
>will sometimes produce the previously-mentioned message.  At other times,
>it will work properly.

Have you tried "pinging" your server?  Or maybe doing an xhost to see
if someone has changed accessibility?  Just a few suggestions.

>While I suspect that this situation results from one or more errors in
>the Tektronix server code, I'd like some way to figure out what's really
>going on.  Can anyone suggest a strategy to help track this down.  Are
>there any contributed X clients that might be run, perhaps from another
>terminal or workstation, that can monitor and interpret network messages?
>If not, could a network analyzer be useful?  Thanks to all who reply.

There is a contrib application called xscope that does what you're
asking for ... you can use it to monitor server-client communication.
There is a README there that explains how to use it and everything.
You can pull it off of expo.lcs.mit.edu.

Fairly useful.

Greer H. Tan
Encore Computer Corporation
gtan@encore.com