Re: problem with X forwarding

From: Ranjeet Shetye (ranjeet.shetye2_at_zultys.com)
Date: 08/25/03

  • Next message: Rio Martin: "OpenSSH 3.6.1 with PAM"
    To: secureshell@securityfocus.com
    Date: 25 Aug 2003 11:40:31 -0700
    
    

    On Mon, 2003-08-25 at 08:58, Rajeev Kumar wrote:
    > Make sure ssh was able to setup X11 tunnel. ssh usually have some entry
    > in /etc/sshd_config file.
    >
    > X11DisplayOffset 10
    >
    > which says how it is going to listen for X11 connection like in above
    > case it is going to listen at port 6010 (offset 10 from std X11 port
    > 6000). SO after you ssh to server then at server try one of this.
    >
    > telnet localhost 6011
    > (Looks like in your case it offset is 11)
    > see if this gives something like this.
    >
    > Trying 127.0.0.1...
    > Connected to localhost.
    > Escape character is '^]'.
    > ^]
    >
    > if not than there is a problem in binding this port, try some other
    > offset value, other than 6000. Also on machine A try
    > xhost + (I don't think if this is a problem as ssh X11 is little different)
    >
    > hope this helps to start debugging.
    >
    > Rajeev
    >
    >
    > Pupeno wrote:
    > > I don't know if this is the right list to post about this problem, but I'm
    > > reaching the desperate state.
    > > I'm ssh from computer A to computer B, running a X application in B expecting
    > > to be shown in A's X server.
    > > X forwarding is enabled in both computers, A and B in both,
    > > /etc/ssh/ssh_config and /etc/ssh/sshd_config.
    > > But when I run the application a get this error:
    > > _X11TransSocketOpen: socket() failed for tcp
    > > _X11TransSocketOpenCOTSClient: Unable to open socket for tcp
    > > _X11TransOpen: transport open failed for tcp/localhost:11
    > > Error: Can't open display: localhost:11.0
    > > Do you have any idea of what may happen ?
    > > In A, I was able to connect when I was running Ark Linux, the problem appeared
    > > when I installed Gentoo so, I may say, the problem is in A since B didn't
    > > suffer any deep change.
    > > Any clue would be nice.
    > > Thanks.
    > > --
    > > Pupeno: pupeno@pupeno.com
    > > http://www.pupeno.com
    > > ---
    > > Help the hungry children of Argentina,
    > > please go to (and make it your homepage):
    > > http://www.porloschicos.com/servlet/PorLosChicos?comando=donar

    Actually I dont think that's the problem.

    His error is: "Error: Can't open display: localhost:11.0"

    Pupeno:

    All X clients use the DISPLAY variable. Your DISPLAY variable is
    currently set to "localhost:11.0", which is typical for an automatically
    set DISPLAY var, and which means that your client will try to connect to
    an X server which is on the same host as the client. You dont want this.
    What you want is for your X Client to connect to a remote X Server.

    You will need to pass the DISPLAY var along with the rest of the
    environment when you initiate the SSH connection e.g. xterm takes a
    "-display displayname"

    in Csh/Tcsh
    setenv DISPLAY "<X-Server-IP-Address>:0.0"
    should work

    For Bash/Ksh/sh
    DISPLAY="<X-Server-IP-Address>:0.0"; export DISPLAY
    should work

    The way you setup the DISPLAY var will depend on how you are creating
    the client-server SSH link.

    Also, use "ssh -X" will ensure that X11 forwarding will take place (as
    long as the server allows it? - not sure on this count). I know you've
    set your sshd_config and ssh_config, but use -X until testing is
    complete.

    Now, on the server side too, you'll need to do a little more work.

    Look into using "xhost" on the X server side, using "xhost +" or "xhost
    + <X-Client-IP-Address>" (more secure). This is needed to let an X
    Client connect to your X Server. Running just "xhost" will tell you wht
    the current settings are.

    HTH

    -- 
    Ranjeet Shetye
    Senior Software Engineer
    Zultys Technologies
    Ranjeet dot Shetye2 at Zultys dot com
    http://www.zultys.com/
     
    The views, opinions, and judgements expressed in this message are solely
    those of the author. The message contents have not been reviewed or
    approved by Zultys.
    

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