Port 4785 (cncp)

IANA assigns port 4785 to cncp: Cisco Nexus Control Protocol.

Registered (user) port, 1024-49151 UDP

Port 4785 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

cncp UDP Cisco Nexus Control Protocol Joseph Swaminathan -

Registry dates for this port: registered 2009-04-01.

Linux: UDP 4785

sudo ss -ulnp 'sport = :4785'

Linux / macOS: which process owns the port

sudo lsof -nP -i :4785

Windows (Command Prompt)

netstat -ano | findstr :4785

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 4785

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

nc -vzu -w 5 HOST 4785

ufw

sudo ufw deny 4785/udp

iptables

sudo iptables -A INPUT -p udp --dport 4785 -j DROP

nftables

sudo nft add rule inet filter input udp dport 4785 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 4785' -Direction Inbound -Protocol UDP -LocalPort 4785 -Action Block

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