...
In order to accomplish this a member will actually need to be listening for connections on both protocols when it initially starts up. We will create a VersionAwareMessenger that contains both a JGroupsMessenger and a NettyMessenger. It can install handlers in both of them, and decide which Messenger to use when sending a message based on the version of the recipient. If a member receives a view that contains no old members that don't support require the old protocol it could shut down the JGroupsMessenger.
...