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Port 4129 (nuauth)

IANA assigns port 4129 to nuauth: NuFW authentication protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
nuauth TCP NuFW authentication protocol Eric Leblond -
nuauth UDP NuFW authentication protocol Eric Leblond -

Registry dates for this port: registered 2007-06.

Check what is listening on port 4129

Linux: is anything listening on TCP 4129?
sudo ss -tlnp 'sport = :4129'
Linux: UDP 4129
sudo ss -ulnp 'sport = :4129'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4129
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4129 '
Windows (Command Prompt)
netstat -ano | findstr :4129
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4129 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4129
From Windows
Test-NetConnection HOST -Port 4129
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4129

Block port 4129 in the firewall

ufw
sudo ufw deny 4129/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4129 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4129 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4129' -Direction Inbound -Protocol TCP -LocalPort 4129 -Action Block
ufw
sudo ufw deny 4129/udp
iptables
sudo iptables -A INPUT -p udp --dport 4129 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4129 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4129' -Direction Inbound -Protocol UDP -LocalPort 4129 -Action Block

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