CentOS 6
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Add Oracle Net Listener
Create Oracle Net Listener that is a network service on Oracle.
[1] Login with the "oracle" user and input a command "netca" like follows.
[oracle@dlp ~]$ netca

[2] Check a box "Listener Configuration" and go next.
[3] Go next.
[4] Set Listner's name. Input any one you like.
[5] This example goes next with keeping default "TCP".
[6] Set a port. This example goes next with keeping default.
[7] If you'd like to create more Listeners, Answer "Yes". This example selects "No".
[8] Configuration completed.
[9] Click "Finish" to quit. After finishing, Confirm the status by "netstat" comand. Then you'll see "tnslsnr" listens 1521 port.