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Author Topic: X display woes  (Read 1102 times)
linuxsurd
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Posts: 3


« on: January 04, 2008, 06:15:09 am »

I'm running VL5.8 (2.6.18.5). I've had minor bumps along the way with one I have not figured out.

When I use telnet (via /usr/X11R6/bin/xterm, Command Prompt X terminal emulator or putty) I get

env shows:
HOSTNAME=vector.linux.net
HOST=vector.linux.net
SESSION_MANAGER=local/vector.linux.net:/tmp/.ICE-unix/9995
DISPLAY=:0.0

I do the following:
[vector] ~ > xhost +
access control disabled, clients can connect from any host
[vector] ~ > xclock
[vector] ~ > telnet xxx.yyy.zzz.com
Trying 172.18.35.8...
Connected to xxx.yyy.zzz.com
Escape character is '^]'.
....
...
> echo $DISPLAY
vector.linux.net:0.0
> xclock
Error: Can't open display: vector.linux.net:0.0

Then I manually set the display to my IP.

> setenv DISPLAY a.b.c.d:0.0
> xclock
Error: Can't open display: a.b.c.d:0.0

I can successfully ssh to some other remote sun host at my work LAN and export my display and run x applications fine. (on the ssh session I notice the DISPLAY is default set to "localhost:13.0".
I can't understand why ssh is fine but my telnet session fails. I am able to run X-apps with telnet from a WinXP-Xceed session on a laptop.

Can someone explain what's happening here with X and telnet on my VL5.8 box ? Is it something to do with the hostname I chose (vector.linux.net) or my X config on VL or something else ?
« Last Edit: January 04, 2008, 07:02:16 am by linuxsurd » Logged
Triarius Fidelis
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Posts: 2399


Domine, exaudi vocem meam


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« Reply #1 on: January 04, 2008, 06:28:18 am »

It has to do with SSH itself. SSH can enable forwarding of X traffic (hence the curious 'localhost:13.0' host name you saw); IIRC, that forwarding functions even behind a firewall or NAT. Telnet does not have that feature. I should point out that 'xhost +' as well as Telnet in general are dangerous to use from a security standpoint.
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"Leatherface, you BITCH! Ho Chi Minh, hah hah hah!"

Formerly known as "Epic Fail Guy" and "Döden" in recent months
linuxsurd
Member
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Posts: 3


« Reply #2 on: January 04, 2008, 07:08:34 am »

Thanks for the reply. I agree about the security issues.

But can you explain why I can run the same telnet session with X using a WinXP/eXceed setup and bring up an X application ? I don't have the ssh daemon running on these remote hosts so I can't use ssh with some hosts. I am within a secure network so I could live briefly with these telnet sessions.
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Triarius Fidelis
Vecteloper
Vectorian
****
Posts: 2399


Domine, exaudi vocem meam


WWW
« Reply #3 on: January 04, 2008, 07:13:48 am »

But can you explain why I can run the same telnet session with X using a WinXP/eXceed setup and bring up an X application ? I don't have the ssh daemon running on these remote hosts so I can't use ssh with some hosts. I am within a secure network so I could live briefly with these telnet sessions.

I haven't used eXceed. Does that offer any special means of tunneling?
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"Leatherface, you BITCH! Ho Chi Minh, hah hah hah!"

Formerly known as "Epic Fail Guy" and "Döden" in recent months
linuxsurd
Member
*
Posts: 3


« Reply #4 on: January 04, 2008, 08:07:14 am »

There's no tunneling for the telnet session that I configured in eXceed (windows). That seems only for ssh sessions.
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