IPP (Internet Printing Protocol)
What is Port 631?
Port 631 is the default port for the Internet Printing Protocol (IPP), the modern standard for network printing. Defined in RFC 8011, IPP is an HTTP-based protocol that provides a standardized way to submit print jobs, query printer status, manage print queues, and discover printers on the network. IPP was developed by the Printer Working Group (PWG) and is the default printing protocol in CUPS (Common Unix Printing System), which is used by macOS and most Linux distributions. IPP supports features like printer capability negotiation, job accounting, access control, and encryption (IPPS over TLS). Unlike older protocols like LPD, IPP can convey rich printer status information including ink levels, paper tray status, and error conditions.
Common Uses
- Network printing on macOS and Linux (CUPS)
- AirPrint wireless printing from Apple devices
- Enterprise print management and monitoring
- Cloud printing and remote print submission
Technical Details
Copy-paste commands to check port 631 (IPP (Internet Printing Protocol)) from your terminal
Test connectivity
nc -zv example.com 631
curl -v --max-time 5 http://example.com:631/
telnet example.com 631
nmap -p 631 -sU -sV example.com
(echo > /dev/tcp/example.com/631) 2>/dev/null && echo "open" || echo "closed"
Open port in firewall
sudo ufw allow 631/tcp
sudo iptables -A INPUT -p tcp --dport 631 -j ACCEPT
sudo firewall-cmd --permanent --add-port=631/tcp && sudo firewall-cmd --reload
Security Considerations
IPP should use IPPS (IPP over TLS) for encrypted communication. Unencrypted IPP can expose printed document contents and user credentials. CUPS has had vulnerabilities that allowed remote code execution. Keep CUPS updated, restrict IPP access to trusted networks, and disable the CUPS web interface (port 631) from external access. Configure authentication for administrative operations.
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