file sharing - external access

Hi everyone,

In order to access files from my Mac (running macOS 10.13), I enabled File Sharing (via SMB) in preferences and forwarded the ports 139 and 445 through my router.

Now, when I attempt access from external Mac via smb://[user name]@[my external IP address]:139 I get a message: "This file server will not allow any additional users to log on. Try to connect again later."

When I try smb://[user name]@[my external IP address]:445, I do get to the login prompt, but then the message "Check the server name or IP address, and then try again."

(btw, screen sharing works fine via vnc://[user name]@[my external IP address]:5900)

Do you have any suggestions?

thanks, geb