we have executed net and nio net channel tests in IPv6 only environments (macOS, linux ubuntu, OL9, windows server 2019) SendPortZero

sample exception

Caused by: java.nio.channels.UnsupportedAddressTypeException
at java.base/sun.nio.ch.Net.checkAddress(Net.java:149)
at java.base/sun.nio.ch.DatagramChannelImpl.send(DatagramChannelImpl.java:825)
at SendPortZero.lambda$testChannelSend$1(SendPortZero.java:102)

So looking at the call flows and the checkAddress
  static InetSocketAddress checkAddress(SocketAddress sa, ProtocolFamily family) {
        InetSocketAddress isa = checkAddress(sa);
        if (family == StandardProtocolFamily.INET) {
            InetAddress addr = isa.getAddress();
            if (!(addr instanceof Inet4Address))
                throw new UnsupportedAddressTypeException();
        }
        return isa;
    }

the family in this instance should be AF_INET6 or java.net.StandardProtocolFamily.INET6 as IPv4 is disabled

The following tests exhibit the same or similar inconsistent behaviour:

java/nio/channels/DatagramChannel/ConnectPortZero.java
java/nio/channels/DatagramChannel/BindNull.java
java/nio/channels/DatagramChannel/Disconnect.java
java/nio/channels/DatagramChannel/AfterDisconnect.java