Since this commit:
https://github.com/infinispan/infinispan/commit/f0fb26d43f0176c165bd10134be7b5feed57c893

... Infinispan is no longer usable in WildFly 9, whose transports are configured to use ForkChannel rather than JChannels. The underlying issue is described in JGRP-1905. The commit above adds a cluster-wide RPC on view change (from org.infinispan.topology.ClusterTopologyManagerImpl.confirmMembersAvailable(), the message for which inevitably arrives on the newly starting node before the requisite fork channel is registered. The RPC eventually times out since Infinispan's RPC dispatcher will wait for a response that will never come.

It is necessary to support internal messaging because that splits the JGroups channel in as many "forks" as you want, one would be owned by Infinispan and others can be dedicated to other tasks.