Listener Not responding

If you lost contact with listener.Try to reload listener from lsnrctl utility.If it doesn't respond. Try to stop it .Still problem persist.

Find the process no of the listener.
# su root

# netstat -tvlnp | grep 1521

  (here 1521 is the port no of tnslsnr)
It will give you the process no

# kill -9 {processno}

  Kill the listener.

Then start the listener.

# su oracle
# . oraenv
#  lsnrctl start 

Still problem persists try once again form the netstat listing.   
   
It may solve your problem