Hello Everyone,
I’m working on a project that involves multicast communication between processes running on different devices within the same network. For all my Apple devices (macOS, iOS, etc.), I am using NWConnectionGroup, which listens on a multicast address "XX.XX.XX.XX" and a specific multicast port.
The issue occurs when a requestor (such as a non-Apple process) sends a multicast request, and the server, which is a process running on an Apple device using NWConnectionGroup (the responder), attempts to reply. The problem is that the response is sent from a different ephemeral port rather than the port on which the multicast request was received.
If the client is behind a firewall that blocks unsolicited traffic, the firewall only allows incoming packets on the same multicast port used for the initial request. Since the multicast response is sent from a different ephemeral port, the firewall blocks this response, preventing the requestor from receiving it.
Questions:
-
Is there a recommended approach within the
NWConnectionGrouporNetwork.frameworkto 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?
Any insights or suggestions on how to account for this behavior and ensure reliable multicast communication in such environments would be greatly appreciated.
Thanks,
Harshal
