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Port 8766 (amcs)

IANA assigns port 8766 to amcs: Agilent Connectivity Service.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
amcs TCP Agilent Connectivity Service Keysight Technologies Inc -
amcs UDP Agilent Connectivity Service Keysight Technologies Inc -

Registry dates for this port: registered 2013-01-16, last modified 2016-09-12.

Check what is listening on port 8766

Linux: is anything listening on TCP 8766?
sudo ss -tlnp 'sport = :8766'
Linux: UDP 8766
sudo ss -ulnp 'sport = :8766'
Linux / macOS: which process owns the port
sudo lsof -nP -i :8766
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':8766 '
Windows (Command Prompt)
netstat -ano | findstr :8766
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 8766 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 8766
From Windows
Test-NetConnection HOST -Port 8766
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 8766

Block port 8766 in the firewall

ufw
sudo ufw deny 8766/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 8766 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 8766 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 8766' -Direction Inbound -Protocol TCP -LocalPort 8766 -Action Block
ufw
sudo ufw deny 8766/udp
iptables
sudo iptables -A INPUT -p udp --dport 8766 -j DROP
nftables
sudo nft add rule inet filter input udp dport 8766 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 8766' -Direction Inbound -Protocol UDP -LocalPort 8766 -Action Block

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