What ports are required for the exam?

The only ports required for your system to connect to the exam console are 80/tcp and 443/tcp.

You can access the web compatibility check tool at https://www.examslocal.com/ScheduleExam/Home/CompatibilityCheck. (You'll want to put in Linux Foundation as the sponsor and then the relevant exam, e.g. "CKA" or "LFCS", for the exam.) As you'll see in that tool, 80/tcp and 443/tcp are required.