java.net.SocketException: Can't assign requested address

Caused by: java.net.SocketException: Can't assign requested address
    at java.net.PlainDatagramSocketImpl.join(Native Method)
    at java.net.AbstractPlainDatagramSocketImpl.join(AbstractPlainDatagramSocketImpl.java:178)
    at java.net.MulticastSocket.joinGroup(MulticastSocket.java:323)
    at com.alibaba.dubbo.registry.multicast.MulticastRegistry.<init>(MulticastRegistry.java:90)
    ... 22 more

This was caused by an IPv6 address being returned from java.net.NetworkInterface.getDefault(). I'm on a Macbook and was using wireless -- p2p0 (used for AirDrop) was returned as the default network interface but my p2p0 only has an IPv6 ether entry [found by running ipconfig].

Two solutions, both of which worked for me (I prefer the first because it works whether you are using a wired or wireless connection)

1. Start the JVM with -Djava.net.preferIPv4Stack=true. This caused java.net.NetworkInterface.getDefault() to return my vboxnet0 network interface -- not sure what you'll get if you're not running a host-only VM.

2. Turn off wireless and use a wired connection