ORA-12541–no listener

Well this just means your listener service is not running.

On a Linux box run the following command:

# lsnrctl

You should get this prompt:

LSNRCTL>

Now type the command:

status

It will show you the status of the service

to start it just type

start

You can check the status now, it should be up and running.

ORA-12541 – Oracle FAQ