Remote Connection

To log in to a remote computer, the easiest option is to just SSH to that computer. Alternatively, you can get a remove window using X11, VNC or proprietory protocols such as earlier versions of Apple Remote Desktop.

X11 over SSH
Think about params in ssh config files! Think about $DISPLAY variable, especially when using sudo

VNC
To start remotely, log in to the remote computer using ssh, then start the VNC server using:

open "/Applications/Applications/Remote Window/OSXvnc.app"

On my Mac at home, this will automatically start the server. Check using ps auxww | grep -i vnc. A process called OSXvnc-server should be listed.

By default, you can only connect from a local connection, so you need to set up an SSH tunnel. Provided that "dagobert" is the remote host, run the following on the client:

ssh -L 5901:127.0.0.1:5900 freek@dagobert

Note that you should specify "127.0.0.1" rather then "localhost" for now, since OSXvnc does not yet support IPv6. Specifying "localhost" resulted in the error "channel 3: open failed: connect failed: Connection refused".

Now you can open VNCThing or any other VNC client to connect to the remote host. To do so, connect to lcoalhost:5901.

Microsoft Remote Desktop Connection (RDC)
Allows you to connect to a Windows desktop machine. Clients exists for Windows and Mac OS.

Apple Remote Desktop (ARD)
Apple Remote Desktop (ARD) allows you to connect to a Mac OS desktop machine.

Since version 2, Apple Remote Desktop uses the VNC protocol, with some added features (such as clipboard sharing).

Disable the "share screen request" dialog
Since Mac OS 10.7 (Lion), the host computer shows a "share screen request" dialog before the screen is shown to a client. This is a great security feature when someone is working on the host. However, for unmanned host (like a server), this is not ideal. This is easy to remedy:
 * 1) Go to "Sharing" in the system preferences.
 * 2) Turn off Screen Sharing
 * 3) Turn on Remote Management.

Remote Management allows users to take control of your computer, including Screen Sharing, but does not request permission before it is done. If you want to use the more advanced remote management (for example to manage all Macs in a classroom), you need to buy Apple Remote Desktop.

External Programs
There are several companies providing

http://www.takecontrolbooks.com/lion-screen-sharing

LogMeIn https://secure.logmein.com/UK/

Teamviewer teamspeak, showmypc