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Port 1027 (6a44)

IANA assigns port 1027 to 6a44: IPv6 Behind NAT44 CPEs.

Registered (user) port, 1024-49151 UDP

Port 1027 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
6a44 UDP IPv6 Behind NAT44 CPEs IESG RFC 6751

Registry dates for this port: registered 2012-08-02.

Check what is listening on port 1027

Linux: UDP 1027
sudo ss -ulnp 'sport = :1027'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1027
Windows (Command Prompt)
netstat -ano | findstr :1027
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 1027

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1027

Block port 1027 in the firewall

ufw
sudo ufw deny 1027/udp
iptables
sudo iptables -A INPUT -p udp --dport 1027 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1027 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1027' -Direction Inbound -Protocol UDP -LocalPort 1027 -Action Block

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