Rsync/Docker
From charlesreid1
rsyncd.conf man page: https://linux.die.net/man/5/rsyncd.conf
Default port for rsync is 873.
The rsync docker container acts as a kind of void function: it modifies (updates) files on disk, based on the traffic on port 873, but it does not result in any traffic being sent out, so it "returns" nothing.
address = 127.0.0.1