Hi,
As many times said we did not reboot or run a sofesticated price of software we just limit the rsync port to ONE connection from a Internet Host. If your router / firewall or what ever keeping the TCP Session alive or your IP is shared typical with a NAT or CGN scenario only one Host can connect. If you are behind a NAT Gateway it fully depends on your gateway how to connect. Our setup is fairly simple. As well we never block or blacklist a IP but as long a 3way handshaked TCP session on rsync is active you can’t establish a 2nd one.