HTTPfy

Port 4320 (fdt-rcatp)

IANA assigns port 4320 to fdt-rcatp: FDT Remote Categorization Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
fdt-rcatp TCP FDT Remote Categorization Protocol Russell P Holsclaw -
fdt-rcatp UDP FDT Remote Categorization Protocol Russell P Holsclaw -

Registry dates for this port: registered 2006-03.

Check what is listening on port 4320

Linux: is anything listening on TCP 4320?
sudo ss -tlnp 'sport = :4320'
Linux: UDP 4320
sudo ss -ulnp 'sport = :4320'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4320
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4320 '
Windows (Command Prompt)
netstat -ano | findstr :4320
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4320 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4320
From Windows
Test-NetConnection HOST -Port 4320
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4320

Block port 4320 in the firewall

ufw
sudo ufw deny 4320/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4320 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4320 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4320' -Direction Inbound -Protocol TCP -LocalPort 4320 -Action Block
ufw
sudo ufw deny 4320/udp
iptables
sudo iptables -A INPUT -p udp --dport 4320 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4320 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4320' -Direction Inbound -Protocol UDP -LocalPort 4320 -Action Block

Related ports

4317OpenTelemetry OTLP gRPC4319skytale4321rwhois4322trim-event

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