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Port 24601 (udpstp)

IANA assigns port 24601 to udpstp: UDP-based IP-Layer Capacity and Performance Measurement protocol.

Registered (user) port, 1024-49151 UDP

Port 24601 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
udpstp UDP UDP-based IP-Layer Capacity and Performance Measurement protocol IESG RFC 9946

Registry dates for this port: registered 2025-09-26.

Check what is listening on port 24601

Linux: UDP 24601
sudo ss -ulnp 'sport = :24601'
Linux / macOS: which process owns the port
sudo lsof -nP -i :24601
Windows (Command Prompt)
netstat -ano | findstr :24601
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 24601

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 24601

Block port 24601 in the firewall

ufw
sudo ufw deny 24601/udp
iptables
sudo iptables -A INPUT -p udp --dport 24601 -j DROP
nftables
sudo nft add rule inet filter input udp dport 24601 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 24601' -Direction Inbound -Protocol UDP -LocalPort 24601 -Action Block

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