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Port 4878 (inst-discovery)

IANA assigns port 4878 to inst-discovery: Agilent Instrument Discovery.

Registered (user) port, 1024-49151 UDP

Port 4878 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
inst-discovery UDP Agilent Instrument Discovery Charles F Steele -

Registry dates for this port: registered 2011-02-15.

Check what is listening on port 4878

Linux: UDP 4878
sudo ss -ulnp 'sport = :4878'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4878
Windows (Command Prompt)
netstat -ano | findstr :4878
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 4878

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4878

Block port 4878 in the firewall

ufw
sudo ufw deny 4878/udp
iptables
sudo iptables -A INPUT -p udp --dport 4878 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4878 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4878' -Direction Inbound -Protocol UDP -LocalPort 4878 -Action Block

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