I / O Error: The network adapter could not establish a connection - with Oracle 11gR2. Connect to SQL Developer

Question

I installed Oracle 11g on a Linux RedHat6 instance, following all the steps mentioned in " http://technologylair.net/2013/08/oracle-11g-installation-linux/#comment-50 " I'm trying to connect to the database from a remote machine using sql developer. But always ends - " IO Error: The Network Adapter could not establish the connection".

The options I use are

Username: sys as sysdba 
Password: <oracle password> 
Hostname: IP address of the server on which Oracle SQL is installed. 
Port: 1521 
SID: testdb

I also created a listener.ora file at "/oracle/product/11.2.0/db_1/network/admin", which was not there before. Whose content is

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /u01/oracle/product/11.2.0/db_1)
      (PROGRAM = extproc)
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_TESTDB))
      (ADDRESS = (PROTOCOL = TCP)(HOST = 173.39.238.15)(PORT = 1521))
    )
  )

DEFAULT_SERVICE_LISTENER = (TESTDB)

I posted this question on dba.stackexchange too. but I need to solve this problem as soon as possible. and need help. So post it here too.

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"lsnrctl status"

( = ( = ( = IPC) ( = EXTPROC_FOR_TESTDB))) TNS-12541: TNS: TNS-12560: TNS:
TNS-00511: Linux : 2: ( = ( = ( = TCP) (HOST = 173.39.238.15) (PORT = 1521))) TNS-12541: TNS: TNS-12560: TNS:
TNS-00511: Linux : 111:

Answer 1

, . ps -ef | grep lsnr, , PID tnslsnr. , lsnrctl start.

Answer 2

ps eaf | grep lsnr , , , .

telnet hostname/IP 1521
Trying hostname/IP ...
telnet: connect to address hostname/IP: Connection refused
telnet: Unable to connect to remote host

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