As described in the doc: Controlling the Default Multicast Address with -u. I changed the default multicast address in my Wildfly server from:
standalone.bat -u=230.12.345.67
to placing it inside the config file standalone.xml. I added this to the system property:
<system-properties>
<property name="jboss.default.multicast.address" value="230.12.345.67"/>
</system-properties>
Which should be picked up by the socket-binding-group:
<socket-binding-group name="standard-sockets" default-interface="public" port-offset="${jboss.socket.binding.port-offset:0}">
...
<socket-binding name="jgroups-mping" port="0" multicast-address="${jboss.default.multicast.address:230.0.0.4}" multicast-port="45700"/>
<socket-binding name="jgroups-udp" port="55200" multicast-address="${jboss.default.multicast.address:230.0.0.4}" multicast-port="45688"/>
However, it seems to be ignored and defaults to 230.0.0.4.