ora 12154 err-client/server connection problems

[padawin]

I'm having problems connecting from my client (8.1.7) to my server (8.1.6) on Redhat 6.2 (machine name linbox). I have two instances on linbox (ora1 and ora2).

I tried connecting from SQL*Plus on client with the following connect strings:
username: ora1dba1
password: ora1dba1
1) connect string: ora1 (ORA 12154:TNS could not resolve service name)
2) connect string: ora1@linbox (ORA 12154)
3) connect string: ora1.linbox (ORA 12545:target/host does not exist)

My init.ora params are:
db_name="ora1"
db_domain=linbox
instance_name=ora1
service_names=ora1.linbox

My server listener.ora is:

SID_LIST_ORA1_LIST =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /u01/apps/oracle/product/8.1.6)
(PROGRAM = extproc)
)
(SID_DESC =
(GLOBAL_DBNAME = ora1.linbox)
(ORACLE_HOME = /u01/apps/oracle/product/8.1.6)
(SID_NAME = ora1)
)
)
ORA1_LIST =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = linbox)(PORT = 1521))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
)
)

My server sqlnet.ora is:
NAMES.DEFAULT_DOMAIN = localdomain
NAMES.DIRECTORY_PATH= (TNSNAMES)

My server tnsnames.ora is:
ORA1.LINBOX =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = linbox)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ora1.linbox)
)
)
EXTPROC_CONNECTION_DATA.LOCALDOMAIN =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)
My client tnsnames.ora is:
# TNSNAMES.ORA Network Configuration File: D:\Oracle\OraRem\NETWORK\ADMIN\tnsnames.ora
# Generated by Oracle configuration tools.

ORA1.LINBOX =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = linbox)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ora1.linbox)
(INSTANCE_NAME = ora1)
(SRVR = DEDICATED)
)
)

ORSERVE =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = orserve)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = orserve)
(INSTANCE_NAME = orserve)
)
)

A) Is my naming methodology wrong? (ie:service_names and db_domain)
B) If my hostname for the server is linbox how should I qualify connections (ie: ora1.linbox?) or what should I change?
C) Do I need a seperate listener for each instance/db on the same machine?

Thanks

[pravin]

In the sqlnet file.

for Host name - give the system IP address.
SID - instance name

u can have multiple instances in one listener file. u have to add the INSTANCE DETAILS BELOW THE FIRST ENTRY.
There also for host name give system ip address.

[padawin]

Got it to work.
Changed init.ora param to services_names=ora1
Changed service_name=ora1 in server tnsnames.ora