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Port 4661 (kar2ouche)

IANA assigns port 4661 to kar2ouche: Kar2ouche Peer location service.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
kar2ouche TCP Kar2ouche Peer location service Andy Krouwel -
kar2ouche UDP Kar2ouche Peer location service Andy Krouwel -

Check what is listening on port 4661

Linux: is anything listening on TCP 4661?
sudo ss -tlnp 'sport = :4661'
Linux: UDP 4661
sudo ss -ulnp 'sport = :4661'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4661
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4661 '
Windows (Command Prompt)
netstat -ano | findstr :4661
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4661 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4661
From Windows
Test-NetConnection HOST -Port 4661
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4661

Block port 4661 in the firewall

ufw
sudo ufw deny 4661/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4661 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4661 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4661' -Direction Inbound -Protocol TCP -LocalPort 4661 -Action Block
ufw
sudo ufw deny 4661/udp
iptables
sudo iptables -A INPUT -p udp --dport 4661 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4661 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4661' -Direction Inbound -Protocol UDP -LocalPort 4661 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.