by default or by the options you chose, 
sqlnet.ora may have any of these entries

NAMES.DIRECTORY_PATH= (TNSNAMES, HOSTNAME, ONAMES)
sqlnet.authentication_services=(NTS)

But, you may not be using the authentication serivces or the oracle names server.
so if you comment it off or remove those entries, you would be all set.

oracle will not do the hostname / domain resolution automatically.
if the host can be 'pinged' it is all set.
may be you can try using LOCALHOST instead of HOSTNAME.DOMAINNAME or IP in your listener.ora.
there are certain init.ora parameters like 
mts_dispatchers = "(protocol=TCP)"
which required a proper tcp/ip connectivity.