Trying to control one ubuntu computer with another ubuntu computer

Hi,

I've got a dell laptop(let's call it M1) and a revo rl70 (M2) both running ubuntu 12.04.

They are both on my home network and use the same router/internet connection.

What I want to do is to be able to control M2 from M1and have M2 respond to mouse and keyboard actions on M1.

I've made sure that desktop sharing is enabled on M2 and installed Remmina on M1 but can't get it to connect at all - I get the message 'Unable to connect to VNC server'.

Anyone know what I need to do to get it working?

Thanks in advance.