lsnrctl statusIf XE is a valid SID, the output should contain something like the following:
If not, then your listener.ora file may not have been created/updated properly. Or possibly you have a more complex environment with multiple listeners, or a single listener which may not be the listener that comes with Oracle 10g XE. For example, I have both 220.127.116.11 and 10g XE installed, but I run only the 11g listener (and disabled the 10g listener).
Services Summary... Service "xe.<yourdomain>" has 1 instance(s). Instance "XE", status UNKNOWN, has 1 handler(s) for this service...
C:\oraclexe\app\oracle\product\10.2.0\server\NETWORK\ADMIN directorybut instead had to alter those files in my
C:\app\<myuserid>\product\11.2.0\<dbhome>\NETWORK\ADMIN directoryso my database listener knows about the XE instance.