When a system is first started, communication daemons make use of the first several available ports on the system. These ports are called anon ports. (These ports are also referred to as: dynamic, private, or ephemeral ports.) The lowest available anon port (lowest port number) is configured through the use of an operating system variable, and is often set by default to a port number lower than 32775. This can cause problems for the Listener, as by default, the Listener application requests TCP port 32775. Therefore, depending on the anon port configuration, it is possible that another service might already be using port 32775 when the Listener attempts to connect.
To resolve this potential issue, you might have to adjust the anon port configuration for your system in order to ensure that the Listener can connect to port 32775. By setting the lowest available anon port to 32776, requesting services such as communication daemons will use ports 32776, 32777, 32778, and so on. This leaves ports 32775 and lower available for the Listeners.
The Internet Assigned Numbers Authority (IANA) has assigned port numbers for various purposes up to the 49000 range, and specifies that the dynamic ports should range from 49152 through 65535.
The following sections provide operating system version-specific information pertaining to the configuration of anon ports to allow the successful operation of the Listener.