Which of the following statements about port forwarding is incorrect?

A$.$

NAT will block the initiative access data flow of the external network, in this case, will need port forwarding to let it reach the server behind NAT

B$.$

The port of HTTP is $8000$

C$.$

DMZ is an easy way to open all ports for one local IP address, but not safe

D$.$

Specific ports can be automatically opened by UPNP protocol and it only supports monolayer NAT