This is probably related to this code:
// if the channelPartitionName is set, we use it to identify the control and
// data channels. Otherwise, we fall back to use groupName
String channelName = (channelPartitionName == null)? channelPartitionName : groupName;
So you need to set the property channelPartitionName in the config file in order to use groupName.
Thanks howard :)
That worked and is more clean than setting the multicast ip/port