From: noemail@please.net   
      
   On Sat, 22 Oct 2022 14:49:11 -0000 (UTC), Rich wrote:   
      
   > Harold Johanssen  wrote:   
   >> On Sat, 22 Oct 2022 03:47:32 -0000 (UTC), Rich wrote:   
   >>   
   >>> Harold Johanssen  wrote:   
   >>>>        I have a Slackware 15.0 host A running a TigerVNC session on   
   >>>> display 1. I can connect to that session from another Slackware 15.0   
   >>>> system with vncviewer tunneled within an sshSSH channel. I can also   
   >>>> ssh into B from a terminal emulator in A.   
   >>>>   
   >>>>        What I would like to do is the following:   
   >>>>   
   >>>>        1. In the TigerVNC session in A launch a terminal emulator and   
   >>>> ssh from it into B.   
   >>>   
   >>> You are telling this ssh here to perform X forwarding, right?  Or are   
   >>> these systems on the same network such that B can contact A without   
   >>> being carried over the ssh tunnel?   
   >>>   
   >>>>        2. At the ssh session in B created above send some graphical   
   >>>> output to the TigerVNC session in A.   
   >>>>   
   >>>>        Step two does not work - I keep getting 'Can't open display:   
   >>>>        A:   
   >>>> 1.0'.   
   >>>>   
   >>>>        I thought that the way to do pull this off consisted of   
   >>>>        executing   
   >>>> the following commands in a terminal emulator in the TigerVNC session   
   >>>> in A:   
   >>>>   
   >>>>        $ export DISPLAY=A:1.0 $ xhost +B   
   >>>   
   >>> The xhost +B has to happen on A.  You need to tell A "allow B to use   
   >>> your display", which is what "xhost +B" does, when run on A.  This   
   >>> above looks like you are doing the xhost on B.   
   >>   
   >>        I don't think I have explained my situation properly. My   
   >> apologies. Let me try again:   
   >>   
   >>        Host A is running an XFCE session that was launched in A with   
   >> vncserver :1, vncserver being the TigerVNC X server.   
   >   
   > Ok, that 'fine point' did not come across well in the original post.   
   >   
   > Is The TigerVNC X server listening on a TCP port for remote X   
   > connections?  Because if it is not, then you can't just do "DISPLAY=*"   
   > on B and have apps on B connect to A (because to connect to A, something   
   > on A has to be listening on the proper TCP port on A).   
      
   	It is. In fact, I can connect to it from anywhere (as long as   
   there is ssh conectivity) with ssvnc - which, in essence, just tunnels   
   vncviewer through an ssh channel.   
      
   >   
   >>        In that session I launched an xterm, and within this xterm I   
   >> executed xhost +B, where B is the IP address if the other host   
   >> involved. Both hosts can reach each other over ssh.   
   >   
   > Reaching each other over ssh does not mean they can reach each other   
   > over X11.  Nor does it mean they are on the same local network.  Are   
   > they on the same local network, or are they separated on different   
   > networks?   
      
   	There are two cases: in the first one they are both in the same   
   local network, and in the second host B accesses host A through a VPN.   
   The behavior is the same in both cases.   
      
   >   
   >>        At this point I expected that when I launch an X application in   
   >> the shell running in B, its output would be displayed in the XFCE   
   >> session in A. It does not, with the diagnostic above.   
   >   
   > If the TigerVNC server does not listen for remote X connections on a TCP   
   > port on A, then this will not work.   
      
   	I does.   
      
   > Instead, try using ssh X forwarding (the -X or -Y options) which tunnel   
   > the X protocol over the ssh connection, and which cause ssh to setup the   
   > proper DISPLAY variable on B for you automatically.   
      
   	I tried with ForwardX11=yes in .ssh/config in both systems, to no   
   avail. At any rate, I had no need for that when the XFCE session in A was   
   launched over Xorg, rather than TigerVNC.   
      
      
   >>        The thing is, until recently I had an XFCE session running on A   
   >> directly on top of Xorg, not TigerVNC's Xvnc - and the steps above   
   >> worked as expected.   
   >   
   > Likely because the real xorg was listening on a TCP port for remote X   
   > connects (usually TCP 6000).  The TigerVNC server may not provide such   
   > support at all, or it may be a CLI option to TigerVNC to cause it to   
   > turn on "listen for external connections".   
      
   	Thanks. I am confused about something here thoug: when I said   
   above that I can vncviewer into A from B, the ports involved in A are (I   
   believe) 5900 and above - in my case, 5901, I think. Are you saying that,   
   besides this, the X server (TigerVNC, in my case) must be listening on   
   port 6000 as well for what I am trying to do to succeed?   
      
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