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?

  • 1
    Your question seems to contradict itself. You state that you're setting up "packet filter" (i.e. a firewall), and then you write that you're "not running any firewall". So there seems to be some information missing here... can you detail what exactly you set up in pf? – jksoegaard May 28 '20 at 23:00
  • Additionally, you say that "all ports are accessible from my other MacBook, but on my PC...ports are NOT accessible." This points to an issue with your PC, not your Mac. Is it possible that the PC (Windows) firewall (or 3rd party virus/security software) has blocked those ports from outgoing traffic? – Allan May 28 '20 at 23:41
  • @Allan good point, I would check it out tomorrow and post any update – Markiian Benovskyi May 28 '20 at 23:52
  • @jksoegaard I meant I was setting up a packet filter, as a try to fix my problem, but it did not, so I reverted my changes and turned off the firewall. My initial setup is without the firewall – Markiian Benovskyi May 28 '20 at 23:52
  • @Allan checked this today, seems I am not able to access any of me machines from my Windows PC, looks like it it realy a problem with closed outgoing connection from my PC. You had a good point, thanks! – Markiian Benovskyi May 29 '20 at 8:10

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.

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