I have a question about the port (nginx+apache)

When you run apache alone, you need 80 ports open.

But when using the nginx+apache combination, do the ports 8181 and 8443 need to be open?

These two ports are closed in my firewall.

But the web is still working.

How can this happen?

It uses Proxypass to forward requests to the 8181 port. Any request on ort 80 will be internally passed to 8181

Your request ----->  Port 80 ------> Proxy pass -----> Redirect 8181 (Internally redirected) -------> load Data from Port 8181