Support for pre JDK 1.4 `DatagramSocketImpl` implementations (DatagramSocketImpl implementations that don't support connected datagram sockets, peeking, or joining multicast groups on specific network interface) has been dropped in this release. Old implementations have not have been buildable since JDK 1.4 but implementations compiled with JDK 1.3 or older continued to be usable up to this release.

Trying to call `connect` or `disconnect` on a `DatagramSocket` or `MulticastSocket` that uses an old implementation will now throw `SocketException` or `UncheckedIOException`. Trying to call `joinGroup` or `leaveGroup` will result in an `AbstractMethodError`.