When I tried to connect to a remote desktop pc (installed with CentOS 4.8) using vncviewer command, I get this error:


This is only happening when I tried to connect to a PC with CentOS 4.8.
Is this a bug of CentOS 4.8? What alternative remote desktop software can I try?

I tried NoMachine software, but I always got an error:

and when i click that error, it expans as:

Please advise what to do. Thanks!

Were you able to connect to it before, ever? Did you try different VNC clients? Check the VNC server side log. What is the software you use on server? x11vnc?
That aside, centos 4.8 is early 2000s...
The possible solution is to try centos 4.8 client in virtual machine with same version.
I think it's still possible to install centos 4.x using vault.centos.org as mirror.

I have not tried to connect to it successfully even once. I tried a linux pc with CentOS 4.6 and a windows 10 laptop as VNC clients. But, all of these failed. When I tried to make CentOS 4.6 PC as server, everything is fine.

How do I check VNC server log?

using rpm command, these are the packages related to vnc softwares:

Our Linux PCs here are used in production line. They are restricted from outside connections. So yum updates don't work. I will try to manually install from vault.centos.org. Thank you so much for your info

Btw, How do I navigate through this website? Which directories should I go?


http://vault.centos.org/4.8/

Thanks!

/var/log/messages probably.
It's great that you have it hidden, and the best would be to not allow it to listen on any external port, only on localhost and you tunnel it over ssh.
Are you trying to look at what's on the running xorg there or make a new session? We need to know what's your VNC server.

the /os/ directory is the release as it was on ISOs, the /updates/ is whatever updates there were for this release. So that would be http://vault.centos.org/4.8/os/x86_64/CentOS/RPMS/ for example for rpms.

if your host box you're connecting to has xorg running and you want to see what's on that display right now, x11vnc does the trick but i don't see it in /os/ there.
if you want to start new GUI session there then it's probably vino or vnc-server. vnc-server would require some set-up to be done to start proper session, and you should probably start it from ssh manually each time.
are you sure your task cannot be achieved by means of terminal?

Thanks man! I saw vnc related logs from messages file. I will now redo my attempt before to see the actual logs.

My apology.. I cannot understand what is xorg.. I am actually a newbie in Linux. How do I know which VNC server I have?

Can you post the related logs? Enclose those in code tags or just paste it at https://paste.ubuntu.com
xorg is X server, if you have any graphical interface on the target computer, it must be running Xorg, so if you want to see that exact display then x11vnc is a solution, if you want to start a new session that would not display on the target monitor, then it's vino or vnc-server.

I installed a newer version of vnc softwares: vnc-4.0-12.el4.1.i386.rpm & vnc-server-4.0-12.el4.1.i386.rpm from http://vault.centos.org/4.8/os/i386/CentOS/RPMS/

I rebooted the PC with CentOS 4.8. Then I tried to issue command vncviewer from a PC client. Then the error return message after the vncviewer command is now like this:


Then, I looked at the /var/log/messages of the CentOS 4.8 server, the related logs is this:


I do not recognize the ip addr 10.33.112.223 . This is neither the address of the PCs I tried.



Oww.. I think now I get it what is xorg. I can actually open another session via vncserver command. But, my problem here is that I cannot display the actual desktop on the target PC which is DISPLAY :0


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EDIT

I think I just mistyped the hostname hehe sorry. I'll reply with the corrected logs in a bit.

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Update:

the return error messages after issuing vncviewer command is still like the original one:


And the new entries of /var/log/messages are still the same with the above messages.

So your objective is to get access to ALREADY running session :0, like, tty7, the physical display of the machine in question, right?
Then I believe x11vnc is what you need, I never tried solving it with vnc-server and always considered it to be a session-creating solution.
As for 10.33.112.223 it is definitely infected and doing bruteforce attacks on LAN, you should investigate this without delay.

So, I will now narrow down the problem. How should I solve this problem with x11vnc? Appreciate for your help!

The safest setup would be running x11vnc under the user who is logged in to the desktop (if any) and running , then accessing it via ssh session like
and then just The point is if you cannot find x11vnc for 4.8 you'll have to take it from sources and build it yourself.

Yes, that's correct. That is my objective. Can you tell me what things I need to do to solve this?

Definitely, I will investigate at once. But, I logged the same time when I issued vncviewer from a PC client.. hmm..

making sure I get it.. So these are the lines I need to execute on the server side:


Then for the client side:

Is this correct? Thank you so much!