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I've just installed Ubuntu 6.06, and I'd like to run x11vnc on it.
I've installed x11vnc, and it appears to run correctly, but I can't connect to it from my Windows box. I've since discovered that Ubuntu installs with all ports closed. How would a newbie open port 5900?
by default, ubuntu doesn't firewall anything (the policies for the chains are all set to ACCEPT)... having no firewall doesn't mean ports are "open"... the ports will be "closed" until something actually listens on a port... once you have something listening on a port, *then* the port is said to be "open"...
so basically, if you haven't changed ubuntu's default iptables firewall settings, then your issue is somewhere else - not with the host's firewall... maybe use netstat to make sure your program is actually listening on the port you expect it to...
I just want port 22 open for ssh, but I can't find out how.
There is no firewall installed by default - so do I need to install one? Can I open it without installing a firewall?
assuming you are referring to a stand-alone box: on ubuntu, even though it includes the iptables/netfilter firewall, no ports are filtered by default - so you simply need to make your ssh daemon listen on port 22 (or any other) and the port will automatically be opened...
My problem was using ssh to access my box. I thought the problem was the port was not open (which it wasn't), but the real problem was that Ubuntu installs only the ssh client (to ssh into other boxes) but not the ssh-server. This is an easy fix:
sudo apt-get install openssh-server
Now ssh server is installed, I can ssh into my box, the port is open, and all is well.
Make sure to read the ubuntuguide.org and secure your ssh-server so root login is disabled, etc.
the two daemons you listed are listening on the loopback interface (127.0.0.1), hence they won't be visible from another box... if you need them to listen on your WAN/LAN interface you'll need to adjust their config files accordingly and then restart them... your firewall's policies are all set to ACCEPT, and your only INPUT rule is also an ACCEPT, so it's not a firewall issue as you aren't doing any packet filtering...