Internet-Security.com TCP port 515 details

TCP port 515 is used by the Line Printer Daemon protocol (LPD/LPR, RFC 1179), the classic UNIX network printing service.
The original Berkeley lpd, LPRng, and modern CUPS (via the cups-lpd compatibility daemon) accept LPD print jobs on 515.
Windows Server provides an LPD Service (under Print and Document Services/Features) that listens on TCP 515 for LPR clients.
Many network printers implement LPD on 515, including HP JetDirect-equipped LaserJet models, Canon imageRUNNER devices, Brother and Ricoh printers, and standalone print servers from vendors like Axis and D‑Link.
UNIX variants such as Solaris and IBM AIX also offer lpd services on 515 for legacy network printing compatibility.
Security: LPD services on 515 have a history of exploits (e.g., remote code execution and spool/file access flaws in BSD lpd, LPRng, and printer firmwares), and exposed 515 can be abused for unauthorized printing.

TCP 515