Well if it was reaching ARDAgent on clent computer, you should be seeing some thing in the secure log.
Have you cehcked to make sure the firewall is off on both computers?
Have you checked to make sure Remote Management is enabled on the client?
Apple Remote Desktop: Configuring remotely via command line (kickstart):
You need an administrator account to use the kickstart utility. To begin using the kickstart utility, use the sudo command, such as:
$ sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/k ickstart -restart -agent
Activate Remote Desktop Sharing, enable access privileges for the users "admin", grant full privileges for the users "admin", restart ARD Agent and Menu extra:
$ sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/k ickstart -activate -configure -access -on -users admin -privs -all -restart -agent -menu
You could ssh try rebooting ARDAgent
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/k ickstart -restart -agent
Or make sure ARDAgent is enabled with
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/k ickstart -activate -configure -access -on