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RE: Info on "Can't open display"




Well first off all if you (I mean any user) are on yahoo, hotmail, excite or
any web based mail, please do not cc to me.  Your mail will not go through,
I block at our server any outgoing and incoming traffic to web based mail
services.  I am against them, for several reasons, basically they 
are a good source of 'Reply To;" for junk mailers.  Second I tell my users
at work why do you need those services if you already got an e-mail account
here, for which I get yelled because I won't let them access those free web
based mail services URLs too ;-)

Anyway.....

> I have been watching this thread closely but I haven't piped up until
> now because I don't really have a lot to offer.
> 
> First off, I have a friend running Windows ME who is encountering
> exactly the same symptoms in every detail.  He does not have ANY VPN
> software installed on his machine.  THIS PROBLEM IS *NOT* restricted to
> VPN users, at least there are quite a few more than 1 (I checked the
> archives) without a VPN client that have the problem. I posted a
> question on behalf of my buddy a month or so ago and received no response.
> Since he isn't on the list and I don't have the problem, I haven't had
> much to say on this one as I figured that I can't be of much help.

I will releasing an updated binary release of XFree86 4.1.0 this weekend.  I
hope it might have some of these socket issues fixded.  Also although in
Cygwin.cf BuilXF86MiscExt is defined, but it XFree86-MISC extension is not
being built.  This will be fixed too, as well some minor things from my TO
DO list.

> 
> I do have a few comments though (OK, I got a little long winded below
> but I think this thread needs to be brought back to the relevant points)
> 
> Kudos to Robert for politely explaining the same things over and over
> due to people not reading what he is saying.
> 
> I will reiterate a couple of points here, and let me point out that if I
> was one of the list regulars/developers I would simply say something
> like "check the archives this has been answered before",

Oh I stopped saying it... because each time I said that, a few users email
to the list and or to me and called me "Asshole" (you will those emails in
mail archive from 1999, 2000).  They expect a full Technical Support
Department here, perhaps better then any software vendor provides.  If you
wish to say it, expect a strong heart and be ready to listen names from a
bunch of childish and rediculous people.

 or maybe I'd
> just provide a one-liner url to the archived message.
> 
> -Telnet to localhost:6000 is, while not complete in all respects, at
> least a decent indication that the VPN client is not doing something as
> basic as blocking all connections to localhost:6000 as some seem to
> imply. Can somebody please explain to me why TerreTermSSH X forwarding
> (see below), displaying remote X clients on the cygwin
> server, and telnet to localhost:6000 all work if the VPN software is
> truly blocking ports.


Actually, What I suspect, though I am not 100% sure, VPN, and in particular
Aventail, does not like Cygwin using UNIXDOMAIN sockets (AF_UNIX).  I think
that is what going on.... BUT I AM NOT SURE BECAUSE I HAVE NOT LOOKED INTO
IT SERIOUSLY.  I DO PLAN TO SIT DOWN THIS WEEKEND AND BEAT MY HEAD ON THIS
ISSUE.

> 
> -Since the problem occurs even if the VPN client is not running, it is
> obviously not some case of the VPN client not allowing split-tunneling
> or something like that.  This has to come down to some interaction with
> the TCP stack.  Then again, why does adding exceptions to the VPN client
> cause things to work even when the client isn't running?


I think adding exception to VPN work because, perpahs, Aventail on
installation modify TCP/IP stack and owns it.... just like AOL 6.0 browser, 
Even if you do not use it, it will screw up other browsers once AOL 6.0 is
intsalled... well not a good example ;-)

CheckPoint SecureRemote modifies NT kernel and also TCP/IP stack, that I
know from their documentation, but it does not give any problems.

> 
> -TeraTermSSH (like any SSH client) can forward X windows connections from
> remote machines.  This requires the SSH client running under 98 to
> connect to localhost:6000 to proxy the X windows request that it is
> forwarding over the encrypted channel from the remote machine.  This has
> been repeated ad nauseum on the list.  TeraTermSSH is a perfectly good
> example of an X Windows client that works.  That being said, it
> certainly would make sense to try another.


What I think Aventail simply won't let you do X forwarding.  Is there a rule
to turn it on off?  I do not know because I do not use it.

> 
> -X servers typically (and yes I just checked mine) listen on ALL local
> IP addresses (ie *.6000). Clients will connect from some random source
> port to port 6000 on $DISPLAY.


That is why I posted in the morning on a Linux box do a netsat -a and you (I
man other poster) will see what is going on.



> 
> I too would have tended to blame the VPN client on this one except for the
> fact that other X clients do work.  Trying another X client and another
> X server would certainly provide more info.

I did not hear more about other xclients.  I asked if he could try clients
from win32-x11 project.  Those clients use only Winsock32, like Hummingbird
Exceed therefore it might give me some clues where to look for problems and
try to find a solution, if I can.

Suhaib

> 
> A couple of things that I haven't seen suggested which may be worth
> trying arei:
> 
> -Running something similar to ktrace or truss (does sysinternals
>  have something similar?) against both client and server.
> 
> -Getting debug versions of client and server and running the client
>  under GDB and/or attaching to the server and following the logic where
>  the connection is failing.
> 
> -As has been suggested by othersi, trying other clients to cygwin server
> and cygwin clients to other server would be very valuable.
> 
> 
> -Steve
> 
> _________________________________________________________
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