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Port 3661 (can-ferret-ssl)

IANA assigns port 3661 to can-ferret-ssl: IBM Tivoli Directory Service using SSL.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
can-ferret-ssl TCP IBM Tivoli Directory Service using SSL Nic Catrambone -
can-ferret-ssl UDP IBM Tivoli Directory Service using SSL Nic Catrambone -

Registry dates for this port: registered 2003-01.

Check what is listening on port 3661

Linux: is anything listening on TCP 3661?
sudo ss -tlnp 'sport = :3661'
Linux: UDP 3661
sudo ss -ulnp 'sport = :3661'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3661
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3661 '
Windows (Command Prompt)
netstat -ano | findstr :3661
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3661 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3661
From Windows
Test-NetConnection HOST -Port 3661
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3661

Block port 3661 in the firewall

ufw
sudo ufw deny 3661/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3661 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3661 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3661' -Direction Inbound -Protocol TCP -LocalPort 3661 -Action Block
ufw
sudo ufw deny 3661/udp
iptables
sudo iptables -A INPUT -p udp --dport 3661 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3661 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3661' -Direction Inbound -Protocol UDP -LocalPort 3661 -Action Block

Related ports

3659apple-sasl3660can-nds-ssl3662pserver3663dtp

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