I have installed fedora 17 on the old desktop computer and put it to DMZ of my NAT network – i.e. whole computer is accessible via public ip address to the internet and could be called "server".
I've allowed SSH connections on firewall – everything works perfect, but there is one huge problem.
Both me and my friend abroad have Windows 7, so we are using putty + xming to forward windows. My computer (on the same LAN as "server") works without any problem (setting putty like this http://www.geo.mtu.edu/geoschem/docs/images/putty_4.jpg).
Friend, however, he can't open any window (xming is running and putty is configured same as in my computer). He can login using putty, I can see him in who output, he can run console programs (e.g. nano), but he cannot start any GUI program. We tried firefox, firefox &, gedit and gedit &. But after issuing the command, nothing happened – just new command prompt and no process created at all… without any error message…
I've also tried it using his account (from my computer) and everything worked…
any ideas, what could cause the problem? is it possible, that some firewall could allow SSH traffic but block X11 forwarding?
Best Answer
This is a little bit of a complicated thing to try doing if you're not that familiar with ssh, X11, and firewalling in general. Have a look at these howtos for guidance on how to do this:
In general you're going to need to configure your SSH client so that all the X traffic being generated from the remote system should tunnel back through the SSH connection. If this isn't setup correctly then the X traffic will try and go over port 6000 from the remote system back to you.
I suggest NOT going the route of allowing the 6000 port traffic, given this would allow others to sniff your network traffic and see X data going back and forth. X in general is good for LAN but not WAN connections.
Also you might want to check out teamviewer. It's free and would allow you to share desktops back and forth. It runs under Linux & Windows and get's around the firewall issues that usually plague people who don't have a fairly deep knowledge of these things.