As part of Security enhancement on TEST database Server (Linux 64 bit) SA changed the permission on /tmp/.oracle to drwxrwx— after the change, listener stopped working, though the process is alive I could see the process id but unable to connect from the client.
Oracle MOS ID: 343253.1 helped us to resolve this issue
LSNRCTL> status
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
TNS-12557: TNS:protocol adapter not loadable
TNS-12560: TNS:protocol adapter error
TNS-00527: Protocol Adapter not loadable
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
TNS-12557: TNS:protocol adapter not loadable
TNS-12560: TNS:protocol adapter error
TNS-00527: Protocol Adapter not loadable
Solution: As root user
$ cd /tmp
$ ls -ld .oracle
$ chmod 01777 .oracle
If owner and group has also changed during the security enhancement implementation then revert it to root:root
Cheers !!!
Raheel
Raheel's Blog 
Hi Raheel,
Preethi Here form Wipro (ex-collegaue). Hope you remember me.
Can I know which version we can see .oracle in /tmp. I had checked in Oracle 10g/11g and 9i as well.
Regards,
Preethi
Hi Preethi,
Yes I remember you. How are you doing ?
Thanks for writing.
Files under /tmp/.oracle or /var/tmp/.oracle are special ‘socket’ files used by local clients to connect via IPC including Listener. It should not be specific to Oracle releases.
Regards
Raheel Syed
I am doing something freaky. I am trying to run a second copy of the same database on the same system in a container.
The container is launched like this:
systemd-nspawn -bD /home/orabox –bind-ro=/usr/lib64 –bind-ro=/home/oracle/Ora12c/db
The database will start, but the listener will not. It seems to be ignoring my listener.ora completely (I have the network/admin directory soft linked to ~oracle/admin-Ora12c – this works for dbs).
I wish I could figure this out.
Hi Raheel
Thanks for sharing
It helped me a lot…