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Port 9878 (kca-service)

IANA assigns port 9878 to kca-service: The KX509 Kerberized Certificate Issuance Protocol in Use in 2012.

Registered (user) port, 1024-49151 UDP

Port 9878 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
kca-service UDP The KX509 Kerberized Certificate Issuance Protocol in Use in 2012
Historically, this service has been referred to as "kca_service", but this service name does not meet the registry requirements. IESG RFC 6717

Registry dates for this port: registered 2012-07-12.

Check what is listening on port 9878

Linux: UDP 9878
sudo ss -ulnp 'sport = :9878'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9878
Windows (Command Prompt)
netstat -ano | findstr :9878
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 9878

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 9878

Block port 9878 in the firewall

ufw
sudo ufw deny 9878/udp
iptables
sudo iptables -A INPUT -p udp --dport 9878 -j DROP
nftables
sudo nft add rule inet filter input udp dport 9878 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 9878' -Direction Inbound -Protocol UDP -LocalPort 9878 -Action Block

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