I changed the /etc/hosts line
127.0.0.1 localhost.domain localhost
127.0.0.1 v204-101.wat.edu.pl v204-101
and it did work
but still I couldn't start lsnrctl and I look to file:
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = v204-101.wat.edu.pl)(PORT = null))
I changed the PORT parameter and its works
Maybe if we would change HOST parameter to localhost.localdomain it would also works without changing file /etc/hosts, but I don't know if it is allowed to change this file because it is generated automatically
I'm having the same problem as the original post (I'm using 11g).
What I don't understand is why this happens from a clean install and default database creation during the install. I've tried setting ORACLE_HOSTNAME but the listener.ora and tnsnames.ora still use NULL for the TCP port.