Require assistance with lab C++-assisted exploitation

Hello everyone,
I learn for the ejpt course.
I need help in lab C+±assisted exploitation I don’t know way after the command " nc -lvp 5555" he can get any result of listening?
I checked the firewall and it’s off.
Thank you.

Check your code: inet_addr (your interface IP) & htons (port). Make sure your port is open for the interface that your VPN is connected to.