HTTPfy

Port 4729 (gsmtap)

IANA assigns port 4729 to gsmtap: GSM Interface Tap.

Registered (user) port, 1024-49151 UDP

Port 4729 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
gsmtap UDP GSM Interface Tap Harald Welte -

Registry dates for this port: registered 2009-01-16.

Check what is listening on port 4729

Linux: UDP 4729
sudo ss -ulnp 'sport = :4729'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4729
Windows (Command Prompt)
netstat -ano | findstr :4729
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 4729

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4729

Block port 4729 in the firewall

ufw
sudo ufw deny 4729/udp
iptables
sudo iptables -A INPUT -p udp --dport 4729 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4729 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4729' -Direction Inbound -Protocol UDP -LocalPort 4729 -Action Block

Related ports

4727fcis, fcis-disc4728capmux4730gearman4731remcap

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