Sorry for the delay in response. As per the suggestion, I tried to used NWPathMonitor() to get all the interfaces I have. And then I create a NWMulticastGroup object passing all the interfaces whose file descriptor is further used to create a NWConnectionGroup object which is used for send/receive operations. However, the issues still occur for the interfaces where the system has taken one of them as the primary interface (let us say we have two interfaces, ethernet and wifi and ethernet is taken as primary interface) and I am unable to send/receive packets through other interfaces (wifi). I have confirmed this behavior using wireshark where I am unable to send/receive multicast packets from the receiver using the other interfaces (wifi), but I am only able to get those messages from the primary interface (ethernet).

Sorry for the delay in response. I am currently using “.reply” method using NWConnectionGroup to reply back to the multicast messages received. Now since I have sent the message from the port “X” and the responder is replying from the port “Y” the firewall blocks the incoming packets from the responder. Is there a recommended approach within the NWConnectionGroup or Network.framework to ensure that responses to multicast requests are sent from the same port used for the request? Are there any best practices for handling multicast responses in scenarios where the requestor is behind a restrictive firewall?