Firewall requirements for vSphere 6.5

I'm planning to setup a vSphere Hypervisor 6.5 in a secured environment and would like to know what outgoing and/or incoming network connections are required for normal operation. I'm planning to buy a license for 6 processors. Incoming/outgoing network connections are on a permissive basis. I would like to avoid the scenario where a VM would suddenly stop working because of a firewall issue.

Thanks!