Port 8088 is for the Wowza Streaming Engine Manager which runs as a separate service to the main server.
You should be able to start it from the command line by going to /Library/WowzaStreamingEngine/manager/bin and running sudo ./startmgr.sh.
You can also set it to run continuously by starting it using the launchctl command. Please refer to the Users Guide for detailed instructions. The Manager is a basic web server so when it is not being used in the browser, it will just sit quietly waiting. When you start the main server from the command line, you will be able to connect to it from the manager. You may notice some errors in the manager if you do shut down the main server and are on one of the pages that automatically refreshes.