I'm not sure I understand the question well (part of that may be that I am not a "TCP/IP expert". How does it list those ports? As listening or established? It sounds like it is just listening which means it is just waiting for a connection. So perhaps your application is just not working or trying to use the port when you are using the NETSTAT command.
There are parms within TCP/IP that restrict port usage by range and parms that reserve ports for certain job names. However, it is not required to reserve the port to a particular job (but it is good practice). Those port assignments can be made in the "MVS" stack within the TCP/IP parms or from the Unix stack (/etc/services).
For more information, please see the various TCP/IP manuals on the z/OS Communications Server bookshelf: http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/Shelves/F1A1BK5.
Dig Deeper on IBM system z and mainframe systems
Related Q&A from Mark Zelden
When initial program load stalls out on a mainframe logical partition, the culprit is often consoles. Connectivity is one of many potential causes. Continue Reading
Programming expert Mark Zelden offers some coding help to a user trying to FTP files from the mainframe to a Linux OS. Continue Reading
Expert Mark Zelden tries to help a reader find out if his z/OS problem is a known vulnerability. When he can't find anything, he explains how to ... Continue Reading