MacOS port become blocked I have tried setting up Packet Filter on macOS 10.15.5. 


I develop software.
I am hosting some services via supervisord.
It has a user interface on port 9001 running to reset/start/stop services.


For all time long it worked well and I was able to access that UI on the local network. I ran a nmap from my Windows PC targeting my development Mac. After this, on nmap my opened ports were displayed as tcpwraped, (i am not running any firewall on my dev mac). I am not able to access my dev machine from the windows pc anymore. It says Unable to connect, though those ports are visible from the nmap.

All ports are accessible from my other MacBook, but on my PC all ports are NOT accessible.

Is there any way to understand what happened?
The reason for me here was my VPN setup, I had to reinstall my Nord VPN, and reconnect in order to be able to access my Mac on local network.
Also, I would suggest using some PacketFilter firewall manager on the Mac machine. I use Murus and it seems to be pretty good for my requirements.
Thanks everyone who helped me to figure this out quickly.