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Port 18181 (opsec-cvp)

IANA assigns port 18181 to opsec-cvp: OPSEC CVP.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
opsec-cvp TCP OPSEC CVP Alon Kantor -
opsec-cvp UDP OPSEC CVP Alon Kantor -

Check what is listening on port 18181

Linux: is anything listening on TCP 18181?
sudo ss -tlnp 'sport = :18181'
Linux: UDP 18181
sudo ss -ulnp 'sport = :18181'
Linux / macOS: which process owns the port
sudo lsof -nP -i :18181
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':18181 '
Windows (Command Prompt)
netstat -ano | findstr :18181
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 18181 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 18181
From Windows
Test-NetConnection HOST -Port 18181
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 18181

Block port 18181 in the firewall

ufw
sudo ufw deny 18181/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 18181 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 18181 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 18181' -Direction Inbound -Protocol TCP -LocalPort 18181 -Action Block
ufw
sudo ufw deny 18181/udp
iptables
sudo iptables -A INPUT -p udp --dport 18181 -j DROP
nftables
sudo nft add rule inet filter input udp dport 18181 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 18181' -Direction Inbound -Protocol UDP -LocalPort 18181 -Action Block

Related ports

18104radpdf18136racf18182opsec-ufp18183opsec-sam

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