Red Hat ENTERPRISE LINUX 5.1 - LINUX ORACLE Tuning Manual page 119

ORA-12547: TNS:lost contact
There can be many reasons for this error. This can happen during the ASM instance start up when the
libaio RPM is not installed on the system.
You can test this by running lsnrctl as the oracle user.
$ lsnrctl start
...
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC)))
TNS-12547: TNS:lost contact
TNS-12560: TNS:protocol adapter error
TNS-00517: Lost contact
Linux Error: 104: Connection reset by peeras
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=centauri)(PORT=1521)))
TNS-12547: TNS:lost contact
TNS-12560: TNS:protocol adapter error
TNS-00517: Lost contact
Linux Error: 104: Connection reset by peer
Make sure the loopback entry in /etc/hosts is not missing when you start the listener:
127.0.0.1 localhost.localdomain
Now try to run lsnrctl as the user oracle again.
localhost
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