Most of the ports are used for diagnostic equipment, things like laser interferometers to measure plasma density or other devices to measure plasma temperatures. Also some ports are used to inject neutral beams for heating.

It is a research reactor, so most of the openings are for instrumentation and ease of upgrades. A production design would have fewer ports.

To add to the others' responses on the purposes of ports, many of them are essentially vacuum pumps to maintain the near-perfect vacuum required for fusion to work.

Very negative take here: To me it looks like premature optimization, some politicians, mathematicians or engineers wet dream, a design that by today is probably known to be suboptimal, that probably caused millions if not billions of euros of unexpected costs, and tens of thousands of hours of migraine for the people who actually have to run and maintain the thing