Oracle 11g http listener configuration for PL/SQL server pages
check tnsnames.ora file

C:\oracle\product\10.2.0\Oracle\NETWORK\ADMIN

ORCL= 
   (DESCRIPTION = 
       (ADDRESS_LIST = 
             (ADDRESS = 
                  (PROTOCAL = TCP)
                  (HOST = 123.456.789.123)
                  (PORT = 1521)
             )
       )
       (CONNECT_DATA = (SID = ORCL))
   )