ESXi must be able to send and receive data from every vSphere Client. If you are attaching your ESXi host to vCenter Server, additional ports will be required. To enable migration and provisioning activities between managed hosts, the source and destination hosts must be able to receive data from each other.
Network port diagram for vSphere 6.x (2131180)
Also, if you are attaching your ESXi host to external storage components, such as an NFS or iSCSI device, or management components, such as a SysLog server, monitoring system, etc, additional ports must be opened on the firewall in those instances.