Failing command is:

# net send doctor2
No command: send
No command: send
  net time              to view or set time information
  net lookup            to lookup host name or ip address
  net user              to manage users
  net group             to manage groups
  net groupmap          to manage group mappings
  net idmap             to manage the idmap id mappings
  net join              to join a domain
  net cache             to operate on cache tdb file
  net getlocalsid [NAME]        to get the SID for local name
  net setlocalsid SID   to set the local domain SID
  net changesecretpw    to change the machine password in the local secrets database only
                        this requires the -f flag as a safety barrier
  net status            Show server status
  net usersidlist       to get a list of all users with their SIDs

  net ads <command>     to run ADS commands
  net rap <command>     to run RAP (pre-RPC) commands
  net rpc <command>     to run RPC commands

Type "net help <option>" to get more information on that option
Valid targets: choose one (none defaults to localhost)
        -S or --server=<server>         server name
        -I or --ipaddress=<ipaddr>      address of target server
        -w or --workgroup=<wg>          target workgroup or domain

Valid miscellaneous options are:
        -p or --port=<port>             connection port on target
        -W or --myworkgroup=<wg>        client workgroup
        -d or --debuglevel=<level>      debug level (0-10)
        -n or --myname=<name>           client name
        -U or --user=<name>             user name
        -s or --configfile=<path>       pathname of smb.conf file
        -l or --long                    Display full information
        -V or --version                 Print samba version information
        -P or --machine-pass            Authenticate as machine account

For now, you can use

echo "Message" | smbclient -M host

I might look into adding this to the net command as well.

Thinking a bit more about this, I think smbclient -M is sufficient. It's not terribly useful, and the whole NetBIOS stuff is pretty icky.

Closing as WONTFIX.

Hm, having "net send" that uses dcerpc to send messages would be neat though.