Port 873 supports rsync daemon and rsync (UDP reference coverage) across distinct transports. Review each protocol before writing firewall or monitoring policy.
Native rsync daemon protocol for file synchronisation.
Repository mirrors, backups, and controlled file-tree synchronisation.
Client to server
Restrict modules and source networks, avoid anonymous writable shares, and tunnel or use SSH where confidentiality is required.
rsync (UDP reference coverage) is documented as a network service convention for port 873 over UDP.
Use this reference entry when identifying or validating systems documented to use 873/UDP.
Varies
Confirm the listening process and current vendor documentation before permitting traffic; a listed convention does not prove the active service or its security posture.