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Port 3866 (dzdaemon)

IANA assigns port 3866 to dzdaemon: Sun SDViz DZDAEMON Port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dzdaemon TCP Sun SDViz DZDAEMON Port Kevin Rushforth -
dzdaemon UDP Sun SDViz DZDAEMON Port Kevin Rushforth -

Registry dates for this port: registered 2003-08.

Check what is listening on port 3866

Linux: is anything listening on TCP 3866?
sudo ss -tlnp 'sport = :3866'
Linux: UDP 3866
sudo ss -ulnp 'sport = :3866'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3866
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3866 '
Windows (Command Prompt)
netstat -ano | findstr :3866
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3866 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3866
From Windows
Test-NetConnection HOST -Port 3866
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3866

Block port 3866 in the firewall

ufw
sudo ufw deny 3866/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3866 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3866 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3866' -Direction Inbound -Protocol TCP -LocalPort 3866 -Action Block
ufw
sudo ufw deny 3866/udp
iptables
sudo iptables -A INPUT -p udp --dport 3866 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3866 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3866' -Direction Inbound -Protocol UDP -LocalPort 3866 -Action Block

Related ports

3864asap-tcp-tls, asap-sctp-tls3865xpl3867dzoglserver3868diameter

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.