Cannot connect to samba server 4.1.3 via smbclient

Hi all,

may be this has been solved by anybody. The samba server is running and I try to test it via smbclient. Here is what I got:

unass@upc20:~> smbclient //upc20/netlogon -Uunass -MASTRO
Enter unass’s password:
Connection to ASTRO failed. Error NT_STATUS_UNSUCCESSFUL

workgroup is, of course, ASTRO and there is no other server around.

Any hints?

Thanks in advance and Merry Christmas to all.