A few questions/comments about java.net.MulticastSocket

[Vitaly Davidovich]

Hi all,

A few colleagues and I were trying to make sense of the
joinGroup(SocketAddress,
NetworkInterface)
<https://github.com/openjdk/jdk/blob/05a764f4ffb8030d6b768f2d362c388e5aabd92d/src/java.base/share/classes/java/net/MulticastSocket.java#L382>
method.  In particular:

   - Why does this take a SocketAddress and then ignores the port in the
   implementation? Any reason it doesn't take InetAddress, which would make it
   clear the port is unnecessary? The deprecated overload of joinGroup takes
   an InetAddress (and is deprecated because it didn't allow specifying the
   network interface).
   - The MulticastSocket class javadoc still talks
   <https://github.com/openjdk/jdk/blob/05a764f4ffb8030d6b768f2d362c388e5aabd92d/src/java.base/share/classes/java/net/MulticastSocket.java#L45>
   about using joinGroup(InetAddress) as the way to join a group.  Should
   probably be updated to mention the non-deprecated overload.
   - Also in the class javadoc, there's a "stray" port variable
   <https://github.com/openjdk/jdk/blob/05a764f4ffb8030d6b768f2d362c388e5aabd92d/src/java.base/share/classes/java/net/MulticastSocket.java#L52>
   that's not defined anywhere in the example.  Since the port is ignored by
   the joinGroup method, what is this port supposed to represent?

Does anyone have any insight into this?

Thanks
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