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Port 10439 (bngsync)

IANA assigns port 10439 to bngsync: BalanceNG session table synchronization protocol.

Registered (user) port, 1024-49151 UDP

Port 10439 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
bngsync UDP BalanceNG session table synchronization protocol Inlab Software GmbH -

Registry dates for this port: registered 2014-05-02.

Check what is listening on port 10439

Linux: UDP 10439
sudo ss -ulnp 'sport = :10439'
Linux / macOS: which process owns the port
sudo lsof -nP -i :10439
Windows (Command Prompt)
netstat -ano | findstr :10439
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 10439

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 10439

Block port 10439 in the firewall

ufw
sudo ufw deny 10439/udp
iptables
sudo iptables -A INPUT -p udp --dport 10439 -j DROP
nftables
sudo nft add rule inet filter input udp dport 10439 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 10439' -Direction Inbound -Protocol UDP -LocalPort 10439 -Action Block

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