No response on port 1521 from server

[DCAdmin_1]

I am not familiar with Tru64 UNIX and I need help as to how to resolve an issue with a server that is online. The server is working fine but a number of external users cannot get a response through the 1521 port. I wanted to know what steps I can take to investigate and resolve with commands and files. Please advise. Thanks in advance.

[Arch_Muthiah]

Hi DCAdmin,

We knew Oracle (if you have) by default uses 1521. and port 1521 conflicts can happen under three circumstances:

1. A non Oracle software uses this port: If the conflict is due to a non Oracle application, please make sure that application is configured to use any port other than 1521.

2. There is already an Oracle8i Database Server on the system: If the conflict is due to an Oracle8i Database Server on the same system, please upgrade the Net8 listener to Oracle Net Listener which is a 9i based listerner software. Please refer to "Oracle9i Application Server Installation Guide, Release 9.0.2" for more details on the upgrade process. Once the upgrade is complete, the listener can be used both by Oracle8i and Oracle9i Database Servers.

3. There is already an Oracle9i Database Server on the system: If the conflict is due to an Oracle9i Database Server on the same system, Infrastructure install can proceed with no additional work. The Oracle9iAS Metadata Repository component of Oracle9iAS Infrastructure will use the same listener.

Archunan

[Arch_Muthiah]

Hi,

You can check which application uses 1521 port and allocate the port accordingly.

But usually 152x ports are by default used by oracle processes.


Archunan

[Ivan Ferreira]

Ensure taht the server is listening to port 1521 with:

netstat -an

Check if the users can ping, traceroute to the server.

Check if the users can connect to another port, like telnet, ssh, ftp.

Ensure that no firewall in front of the server is blocking the access.

Check with the netstat the status of a connection with one of the clients.

[DCAdmin_1]

I am not familiar with the oracle commands to check certain things. I was hoping to look at certain files and processes. The netstat -an displayed some things but I wasnt sure what I should be concerned with. Anything else?

[Steven Schweda]

Does "a number of external users" mean _all_
users or _some_ users?

"cannot get a response through the 1521 port"
Doing what? What is the result of trying
whatever you are trying? Error message?

If a process is listening on port 1521, then
output from "netstat" should include a line
like:

tcp 0 0 *.1521 *.* LISTEN

For a quick test, you can try to connect to
a server on port 1521 using a Telnet cammand
like:

telnet 1521

If you get a response like "connection
refused", then there's no server listening on
that port.

As usual, it might help if you show what you
actually do and what the response actually
is, rather than just giving vague
descriptions.

[DCAdmin_1]

According to one of our other sys admins, he ran the route add command, route add default ###.##.##.##. This has resolved this issue before, come to find out. The question was asked why doesnt this set up stay permanently after reboot? Does anyone know how to keep this permanent?

[Vladimir Fabecic]

/etc/routes
See man pages.

[Arch_Muthiah]

DCAdmin,

Do you have Oracle/OracleAS in your env?

Archunan

[Arch_Muthiah]

Incase if you have more than one oracle Listner setup, check what are the other port number specified in the listner file.

Do you have your 1521 port specified for any listner?

Are your using Oracle or OracleAS.

and are there any services specified to use port 1521 ? in your /etc/services file.

Archunan

[DCAdmin_1]

Archunan Muthiah,

I do not see that in my env.

[DCAdmin_1]

Archunan,

We are running Oracle applications...I believe 10g. The port 1521 is not listed or assigned to anything under /etc/services



Incase if you have more than one oracle Listner setup, check what are the other port number specified in the listner file.

Do you have your 1521 port specified for any listner?

Are your using Oracle or OracleAS.

and are there any services specified to use port 1521 ? in your /etc/services file.

Archunan

[Arch_Muthiah]

DCAdmin,
Ok you have oracle 10g.

We don't know your DBA created (manually or automatically) "$ORACLE_HOME/network/admin/listener.ora" during installation.

So make you have this listener.ora file in the above directoty. and this file will have all listener details with host name, ip address and port number details ....like this...

LISTENER_SERVER01 =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = server01-v)(PORT = 1521))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 123.123.123.1)(PORT = 1521))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
)
)

If this file not available, you can create it using Oracle Net Configuration Assistant (netca).

Make sure you have 1521 port allocated for all the listener, if not edit the port number and add 1521 as the port

After this, check for "tnsnames.ora" file in each client node which wants to access the oracle server.

if you look into this tnsnames.ora file, it look like this...db01g =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = server01-v)(PORT = 1526))
(ADDRESS = (PROTOCOL = TCP)(HOST = server02-v)(PORT = 1526))
(LOAD_BALANCE = yes)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = db01g.ORACLE-BASE.COM)
)
)
...
...
LISTENERS_db01g =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = server01-v)(PORT = 1526))
(ADDRESS = (PROTOCOL = TCP)(HOST = server02-v)(PORT = 1526))
)


The LISTENER_db10g entries are referenced by the SID.LOCAL_LISTENER and SID.REMOTE_LISTENER parameters in the "spfile".

Run the following commands on all nodes to start the GSD daemon and the listener:

$CRS_HOME/bin/gsdctl start
$ORACLE_HOME/bin/lsnrctl start

then check your all oracle process are running using "ps -eaf" command. If you find all oracle process, then all client can connect thru 1521 to the oracle server.


Archunan