How to sync between two machines when sharing connection

I have a Mac Pro with two ethernet ports, and I have it sharing the line to the outside world (Ethernet 1) with my Macbook Pro using the Mac Pro Ethernet 2. When I attempt to use a direct connection to sync databases between the two, I get the error message:

“The local application and the remote application are the same. Please check the remote address and try again.”

When I try using only wi-fi connections on both machines, I get the same error.

I use the same account name for both machines.

Any ideas?

Please start a Support Ticket. Thanks.