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Port 270 (gist)

IANA assigns port 270 to gist: Q-mode encapsulation for GIST messages.

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

Port 270 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
gist UDP Q-mode encapsulation for GIST messages - RFC 5971

Check what is listening on port 270

Linux: UDP 270
sudo ss -ulnp 'sport = :270'
Linux / macOS: which process owns the port
sudo lsof -nP -i :270
Windows (Command Prompt)
netstat -ano | findstr :270
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 270

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 270

Block port 270 in the firewall

ufw
sudo ufw deny 270/udp
iptables
sudo iptables -A INPUT -p udp --dport 270 -j DROP
nftables
sudo nft add rule inet filter input udp dport 270 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 270' -Direction Inbound -Protocol UDP -LocalPort 270 -Action Block

Related ports

268td-replica269manet271pt-tls280http-mgmt

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