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Multicast Ipv4 and Ipv6 in Java / Kotlin

Oct 27, 2023 18:02:00 UTC

I recently ran into a peculiarity of multicast in Java / Kotlin. I was using a MulticastSocket: [https://docs.oracle.com/javase/8/docs/api/java/net/MulticastSocket.html](https://docs.oracle.com/javase/8/docs/api/java/net/MulticastSocket.html) and trying to ensure that it winds up bound to either an Inet4Address or Inet6Address. It turns out that even if I did something like: ``` val multicastSocket = MulticastSocket(InetSocketAddress("0.0.0.0", MULTICAST_DEFAULT_PORT)) assert(multicastSocket.localAddress is Inet4Address) ``` The assertion could fail. Similarly if I did: ``` val multicastSock ...