LISTENER =
 (DESCRIPTION_LIST =
  (DESCRIPTION =
   (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
   (ADDRESS = (PROTOCOL = TCP)(HOST = 10.1.111.123)(PORT = 1521))
  )
 )

ADR_BASE_LISTENER = /opt/oracle
tnsnames.ora

ORCL =
 (DESCRIPTION =
  (ADDRESS = (PROTOCOL = TCP)(HOST = 10.1.111.123)(PORT = 1521))
  (CONNECT_DATA =
   (SERVER = DEDICATED)
   (SERVICE_NAME = orcl)
  )
 )