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Port 1761 (cft-0)

IANA assigns port 1761 to cft-0.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cft-0 TCP cft-0 Martine Marchand -
cft-0 UDP cft-0 Martine Marchand -

Check what is listening on port 1761

Linux: is anything listening on TCP 1761?
sudo ss -tlnp 'sport = :1761'
Linux: UDP 1761
sudo ss -ulnp 'sport = :1761'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1761
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1761 '
Windows (Command Prompt)
netstat -ano | findstr :1761
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1761 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1761
From Windows
Test-NetConnection HOST -Port 1761
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1761

Block port 1761 in the firewall

ufw
sudo ufw deny 1761/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1761 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1761 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1761' -Direction Inbound -Protocol TCP -LocalPort 1761 -Action Block
ufw
sudo ufw deny 1761/udp
iptables
sudo iptables -A INPUT -p udp --dport 1761 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1761 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1761' -Direction Inbound -Protocol UDP -LocalPort 1761 -Action Block

Related ports

1759spss-lm1760www-ldap-gw1762cft-11763cft-2

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