So I'm learning several topics when it comes to networking right now and more so with my Mac. I was wondering if anyone could tell me if it is typical for ports 137, 138, and 5353 to be open ports on my MBP even with the firewall blocking all incoming connections? Any explanation as to their uses is also greatly appreciated and much thanks in advance to anyone able to explain them to me!
MacBook Pro 15″, macOS 12.6
Apple uses different zero configuration tools to discover services on a local area network. Bonjour runs mDNSResponder which listens on port 5353 and implements Multicast DNS and DNS service discovery. There is also a NetBIOS daemon that interacts with NetBIOS networks and interacts with mDNSResponder via ports 137/138. These help it to detect networked printers, PCs on the network, and SMB service requests. These are transparent to the Firewall at any setting as they are important to normal macOS function.
In the Terminal:
man mDNSResponder
man netbiosd
Apple uses different zero configuration tools to discover services on a local area network. Bonjour runs mDNSResponder which listens on port 5353 and implements Multicast DNS and DNS service discovery. There is also a NetBIOS daemon that interacts with NetBIOS networks and interacts with mDNSResponder via ports 137/138. These help it to detect networked printers, PCs on the network, and SMB service requests. These are transparent to the Firewall at any setting as they are important to normal macOS function.
In the Terminal:
man mDNSResponder
man netbiosd
Hey, Thanks a lot man! Occasionally search results are so scattered amongst operating systems and this was helpful!
UDP ports 137, 138, 5353