[oracle@oracle11g admin]$ cat listener.ora 
# listener.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = oracle11g)(PORT = 1521))
    )
  )
SID_LIST_LISTENER =  
(SID_LIST =  
  (SID_DESC =  
  (GLOBAL_DBNAME = orcl)
  (SID_NAME = orcl)
  )
)
ADR_BASE_LISTENER = /u01/app/oracle

强行注册

登录数据库：
$sqlplus / as sysdba
显示服务名：
SQL>show parameter service_names
强制注册服务：
SQL>alter system register;
查看监听状态：
$lsnrctl status