Re: problem with X forwarding

From: Ranjeet Shetye (
Date: 08/25/03

  • Next message: Rio Martin: "OpenSSH 3.6.1 with PAM"
    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
    > 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:
    > >
    > > ---
    > > Help the hungry children of Argentina,
    > > please go to (and make it your homepage):
    > >

    Actually I dont think that's the problem.

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


    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

    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.


    Ranjeet Shetye
    Senior Software Engineer
    Zultys Technologies
    Ranjeet dot Shetye2 at Zultys dot 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.

  • Next message: Rio Martin: "OpenSSH 3.6.1 with PAM"

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