I suggest that -v option (verbose) would be added to smbclient. For example,
I configured my smb.conf and testparm validated it as valid. However, smbclient
-L says "protocol negotiation failed". I would like to know what exactly failed
in what protocol negotiation, but smbclient doesn't have any -v switch.
use a nigher debug level.
to be more specific, use --debuglevel=[0 - 10] depending on
how much you want to see.