A few questions/comments about java.net.MulticastSocket

[Vitaly Davidovich]

Thanks Alan.

On Tue, Jan 19, 2021 at 1:57 PM Alan Bateman <Alan.Bateman at oracle.com>
wrote:

> On 19/01/2021 18:36, Vitaly Davidovich wrote:
>
> 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).
>
> That was an API mistake in Java 1.4. When DatagramChannel was updated to
> support joining multicast groups (in Java 7) it was able to get the
> parameters right.
>
Would it make sense to make a note of this aspect in joinGroup's javadoc?

>
>
>
>    - 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?
>
> Yes, the javadoc needs some TLC.
>
> -Alan
>
>
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