In Ubuntu, there are many remote desktop utilities: tightvnc, vncserver, vnc4server(Xvnc), x11vnc, vino( the vnc which Feisty build in ).
The difference between them is to open a new display or connect to the existing one.

The easiest way for building server is choose the System -> Preference -> Remote Desktop and set up your settings.
But it's the solution in Gnome.

I use E17 as my window-manager, and don't know how to set up the vino-preference.
So, I've tried vncserver, vnc4server and finally x11vnc.

x11vnc is a server which let you control desktop environment remotely. It needs to start up X window first and use this display session( usually :0 ).
The most common problem is Xlib find display:0 error as .Xauthority isn't well set up.
When you see the tips and tried

ps -wwaux|grep auth

You'll find the existing session's auth. Here's the file used by Enlightenment 17.

x11vnc -auth /var/:0.Xauth

Also, you need a password for authentication of remote connection.
Just exec vncpasswd to generate ~/.vnc/passwd and use -rfbauth $HOME/passwd.
Or use -usepw. A .x11vncrc will be helpful.

As the client side, you can just use RealVnc's free client to connect the server.

ps. I found some errors as :

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Google it and find the solution:

sudo xhost local:kimk

But I still don't understand why.