Java Database Connectivity (JDBC)

Hello,
I am trying to run my first JDBC application (using the thin driver) -- the Oracle DMLSample example. But I am getting a connection error related to SID:
"Listener refused the connection with the following error: ORA-12505, TNS:listener does not currently know of SID given in connect descriptor The Connection descriptor used by the client was:(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(PORT=1521)(HOST=127.0.0.1))(CONNECT_DATA=(SID=dmsdm)))"


Here is my setup:
I have started the listener -- here is the result of "lsnctl start" command:
-----------------------------------------------------------------------
Starting /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin/tnslsnr: please wait...
TNSLSNR for Linux: Version 10.2.0.1.0 - Production
System parameter file is /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin/listener.ora
Log messages written to /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC_FOR_XE)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=qella.array.ca)(PORT=1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC_FOR_XE)))
STATUS of the LISTENER
Here is the listener.ora file content
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date 25-MAY-2007 09:46:36
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Default Service XE
Listener Parameter File /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin/listener.ora
Listener Log File /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/log/listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC_FOR_XE)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=qella.array.ca)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
------------------------------------------------------------------------

The application is built with JDevloper and tries to connect to the DB (located on the same Linux machine where the Oracle installed) with the following parameters:

HostName = qella.array.ca
SID = dmsdm
Port = 1521
UserName = hr
Password = hr

---------------------
Here is the listener.ora file contents:
----------------------------------------------------
# listener.ora Network Configuration File:

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/product/10.2.0/server)
(PROGRAM = extproc)
)
)

LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
(ADDRESS = (PROTOCOL = TCP)(HOST = qella.array.ca)(PORT = 1521))
)
)

DEFAULT_SERVICE_LISTENER = (XE)
-----------------------------------------------------------

Here is the listener.ora file contents:
-----------------------------------------------------------
# tnsnames.ora Network Configuration File:
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = qella.array.ca)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
)
)

EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)
-----------------------------------------------------------

My questions:
1. What is wrong/missing in my setup?
2. In case I don't remember the SID -- how can I find it?

Thanks very much!

Mark.