This issue is related to
BOOKKEEPER-896 which introduced the ability to use Netty built-in local channels.
The idea is to disable Bookie networking for networkless JUnit testing.
We can introduce a "disableServerSocketBind" option to skip server-side bind at BookieNettyServer#listenOn
Another use case is to use BookKeeper as write-ahead log for single machine applications
ZookKeeper still needs network but this is another issue