Port 271 (pt-tls)

IANA assigns port 271 to pt-tls: IETF Network Endpoint Assessment (NEA) Posture Transport Protocol over TLS (PT-TLS).

Well-known (system) port, 0-1023 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

pt-tls TCP IETF Network Endpoint Assessment (NEA) Posture Transport Protocol over TLS (PT-TLS) IESG RFC 6876

Registry dates for this port: registered 2012-07-31.

Linux: is anything listening on TCP 271?

sudo ss -tlnp 'sport = :271'

Linux / macOS: which process owns the port

sudo lsof -nP -i :271

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':271 '

Windows (Command Prompt)

netstat -ano | findstr :271

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 271 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 271

From Windows

Test-NetConnection HOST -Port 271

ufw

sudo ufw deny 271/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 271 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 271 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 271' -Direction Inbound -Protocol TCP -LocalPort 271 -Action Block

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