I searched high and low for this answer, so I'm hoping this will be useful to someone else.
From macOS, I started receiving the error:
mount_smbfs: server connection failed: Socket is not connected
The following is the command (and I used may variations thereof):
mount -t smbfs -o nosuid,-d=755,-f=644,soft smb://username:password\!@myserver.local/Share /local/path/to/Share
I'm connecting to a Linux server and most of the information I've read relates to macOS and Windows.