I have only 1 instance running in this server.

I have only 1 listener file.

[oracle@oracle10g admin]$ cat listener.ora
# listener.ora Network Configuration File: /u01/app/oracle/product/10.1.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = orcl)
(ORACLE_HOME = /u01/app/oracle/product/10.1.0/db_1)
(PROGRAM = extproc)
)
)

LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = oracle10g.pdcindscape.com)(PORT = 1521))
)
)
)