|Have you checked, whether the SSH server is running?|
Open a terminal console on the Ubunto box.
sudo rcsshd status
I'm not sure whether this command do exist on Ubuntu, if not, try this in the terminal window.
sudo netstat -tapn | grep '\:22'.
If there is nothing listed like:
tcp 0 0 0.0.0.0:22 0.0.0.0:* listen
you have to configure your system to use ssh server first.
If ssh server is running, you might have to check, whether port 22 is blocked by your firewall.
Please send a reply, if you solved the problem !!!