Using VNC from a Windows box, I sometimes find that Apple Remote Desktop (ARD) crashes, and I can’t reconnect. So, I came across a nugget[*] that restarts ARD for me, so that I can reconnect.
SSH in as root and..
cd /System/Library/CoreServices/RemoteManagement cd ARDAgent.app/Contents/Resources/ ./kickstart -activate -restart -agent
.. which works for me!
Or, a one-liner:
/System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -restart -agent
[*]I had a link to an Apple Discussions thread where I got this “nugget”, but that has since become invalid.