You can start the WebCC server directly from a terminal. This is usually not practical for a production environment, but it can be very useful when troubleshooting problems. You can view the output of the server directly in the command line as it launches and handles requests.
In a command line, enter the following command:
$ "/Applications/Toon Boom Harmony 20 [Edition]/Harmony [Edition].app/Contents/tba/macosx/bin/webcc.sh"