JDBC oracle listener random port

Question

I have an issue with our listener trying to assign random ports to JDBC connections.

We have a 19c oracle db running on a RHEL server with two ports opened 1523 and 1524. When application tries to connect using JDBC it connects on one of the above ports assigned to listener but then we can see in the log that listener assigns some random port from 30000-65000 range.

...(HOST=`_jdbc_`)(USER=xyz))) * (ADDRESS=(PROTOCOL=tcp)(HOST=1.2.3.4)(PORT=60579)) * establish * hostname * 0

but the application doesn't receive information about connection as those random ports are not opened.

Any idea how we can set specific ports to be used rather than those random ones?

Answer 1

The port in the log is the port on the client machine, not the port on the server. Client ports are essentially random, in the range you specified, as they are assigned sequentially by the client operating system on demand for outgoing connections. They cannot be set.

For example, running netstat -an from my client after making a database connection reveals the following:

Active Connections

Proto  Local Address          Foreign Address     State
TCP    10.89.0.116:52861      10.89.0.65:1521     ESTABLISHED

Note that the server port is still 1521, and my client port is in the same high range you specified. Run netstat -an on either your client or database server and you should be able to confirm the actual port numbers in use at each end of the connection.

Answer 2

You firewall needs to be configured to allow those random ports when the request is initiated by the server. That's how it works. The port you have configured at the listener is for the exclusive use of the listener itself, to receive connection requests. That port is not used for the ongoing communication between the client and the server process. When the listener confirms that it knows about the requested database, it spawns a server process and tells the client what port to use to communicate with that process. The listener only receives the connection request and sets up the connection. Once that connection is set up, the listener is out of the picture. You can even shut down the listener, and existing connections will be unaffected.

As an aside, why have you assigned two ports to the listener, and why are neither one on the default of 1521? One single listener, with the default name of LISTENER, using the single default port of 1521, is quite capable of -- indeed, was designed to - service multiple databases of multiple versions running from multiple ORACLE_HOMEs.