Port 5351 (pcp)

IANA assigns port 5351 to pcp: Port Control Protocol.

Registered (user) port, 1024-49151 UDP

Port 5351 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference

pcp UDP Port Control Protocol IESG RFC 6887

Linux: UDP 5351

sudo ss -ulnp 'sport = :5351'

Linux / macOS: which process owns the port

sudo lsof -nP -i :5351

Windows (Command Prompt)

netstat -ano | findstr :5351

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 5351

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 5351

ufw

sudo ufw deny 5351/udp

iptables

sudo iptables -A INPUT -p udp --dport 5351 -j DROP

nftables

sudo nft add rule inet filter input udp dport 5351 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 5351' -Direction Inbound -Protocol UDP -LocalPort 5351 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.