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Port515— LPD / line printer daemon

TCPSystem

TCP 515 is the LPD (line printer daemon) protocol from Unix history, kept alive for legacy printers and enterprise print servers. New deployments should prefer IPP (631) or raw jetdirect (9100).

Registry assignments, software defaults and local listeners are different things. A port number alone does not identify or secure a service.

Configuration and troubleshooting

For LPD print failures: the LPD service is provided by cups-lpd (typically activated via xinetd or a systemd socket unit), so confirm it is running; match the client queue name (`lp -d`) to the printer. Allow TCP 515. For stuck queues, `lpstat -o` lists jobs and `cancel -a` clears them.

Important limitations

LPD has no authentication or encryption, and its implementations carry a long vulnerability history. Keep it on trusted LANs; cross-network printing should use IPPS (631 with TLS).

Read-only checks: run on the server host

Choose the commands for your OS. Check TCP and UDP separately. No result is not a lasting availability guarantee; inspect host and container separately.

Linux

sudo ss -ltnp 'sport = :515'

macOS

sudo lsof -nP -iTCP:515 -sTCP:LISTEN

Windows PowerShell

Get-NetTCPConnection -LocalPort 515 -State Listen

Sources and review

Sources checked on:

This review covers the explanations and sources on this page, not your device or every community software entry below.

Software Using This Port (2 software)

Community software entries: links are references, not individual verification.

LPD (Line Printer Daemon)

Printing

CUPS Print Service

UnixPrintingSystemLPDProtocol

Reference link ↗

Usage Suggestions

  • Before using port 515, please confirm it is not occupied by other services
  • If you encounter port conflicts, consider using other ports or stopping the occupying service

Frequently asked questions

What is port 515 used for?

Port 515 sits in the System category. This page lists the registered purpose and the software commonly associated with it; to see what is actually listening on a specific machine, check the process with ss/netstat.

Is port 515 TCP or UDP?

The registered protocol on this page is TCP. The same number behaves independently on each protocol: TCP may be listening while UDP is idle, so check them separately.

How do I check if port 515 is in use?

On Linux: sudo ss -tlnp 'sport = :515' for an exact port match. On macOS: sudo lsof -nP -iTCP:515 -sTCP:LISTEN. On Windows PowerShell: Get-NetTCPConnection -LocalPort 515 -State Listen. A listener counts as confirmed only when you can see the bind address and process name; without root/admin you will not see other users' processes.

Is port 515 secure? Should I open it in my firewall?

A port number has no inherent security — it depends on whether the listening service is correctly configured and whether it needs exposure at all. Keep loopback/internal-only services firewalled; where public access is required, pair it with source restrictions, VPN or authentication. The caution section on this page lists port-specific risks.

Quick Info

Port
515
Protocol
TCP
Categories
System
Usage Status
2 software in use

Related Ports

Port 631TCP
Port 9100TCP

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