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Port 1764 (cft-3)

IANA assigns port 1764 to cft-3.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cft-3 TCP cft-3 Martine Marchand -
cft-3 UDP cft-3 Martine Marchand -

Check what is listening on port 1764

Linux: is anything listening on TCP 1764?
sudo ss -tlnp 'sport = :1764'
Linux: UDP 1764
sudo ss -ulnp 'sport = :1764'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1764
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1764 '
Windows (Command Prompt)
netstat -ano | findstr :1764
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1764 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1764
From Windows
Test-NetConnection HOST -Port 1764
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1764

Block port 1764 in the firewall

ufw
sudo ufw deny 1764/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1764 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1764 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1764' -Direction Inbound -Protocol TCP -LocalPort 1764 -Action Block
ufw
sudo ufw deny 1764/udp
iptables
sudo iptables -A INPUT -p udp --dport 1764 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1764 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1764' -Direction Inbound -Protocol UDP -LocalPort 1764 -Action Block

Related ports

1762cft-11763cft-21765cft-41766cft-5

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