Samba uses a NetBIOS port (137, 138 or 139 probably). If the port is blocked, no connection to samba server can be made from the remote machine, which can result in the error message you're seeing.
Furthermore, I'm not sure, but you may need to connect to localhost:901 on the smb machine itself, rather than
connecting to SWAT from the 2nd machine.
Maybe
http://bilbos-stekkie.com/swat/starting_swat_us.php
has some clues for you as well.