Internet-Security.com TCP port 9101 details

Bacula Director (bacula-dir) uses TCP port 9101 by default for its control service in Bacula backup deployments.
Bareos (the Bacula fork) also defaults to TCP 9101 for its Director service (bareos-dir).
Multi-port network print servers often map additional raw-print queues to 9101 (and 9102), for example HP JetDirect multi-port models and AXIS print servers, where 9101 typically serves the second printer port.
Various printer adapters from vendors like Epson and Canon similarly expose a second RAW printing queue on 9101 in multi-port configurations.
Security note: RAW printing services on ports 9100/9101/9102 have been abused to push arbitrary print jobs or data to printers (e.g., via tools like PRET) when exposed to untrusted networks.

TCP 9101