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// Network services

Port 4361: NavCom Discovery and Control Port

Port 4361 is assigned by IANA to nacnl (NavCom Discovery and Control Port).

4361

How nacnl works

Network services
client:4361nacnlresponse client:4361nacnlresponse

The client sends a request to port 4361 and the nacnl service answers.

Transport
UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Network services
01 Security

Is port 4361 dangerous?

We have no specific security note for port 4361. Its risk depends on the program actually listening on it. General advice for network services services:

  • Answer only the networks that need the service (no open resolvers, relays or reflectors).
  • UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
  • Disable legacy test services that have no use in production.
02 Registry

IANA registry entries for port 4361

ServicePortTransportDescriptionReferenceUpdated
nacnl 4361 UDP NavCom Discovery and Control Port - 2009-03-18
-4361-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 4361, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4361'      # process listening on 4361
sudo lsof -nP -i :4361

macOS

sudo lsof -nP -i :4361

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4361 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4361
netstat -ano | findstr :4361

From another machine

nmap -p 4361 -sV <host>
sudo nmap -sU -p 4361 <host>
nc -zv <host> 4361

Block it in the firewall

sudo ufw deny 4361/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4361" -Direction Inbound -LocalPort 4361 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 4361 used for?

Port 4361 is assigned by IANA to nacnl (NavCom Discovery and Control Port).

Is port 4361 TCP or UDP?

Port 4361 is registered for UDP.

Is it safe to open port 4361?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Answer only the networks that need the service (no open resolvers, relays or reflectors).

How do I check if port 4361 is open?

On Linux run "ss -ltnup 'sport = :4361'", on macOS "lsof -nP -i :4361", and on Windows "netstat -ano | findstr :4361" to see the local process. From another machine, "nmap -p 4361 <host>" shows whether it is reachable.

05 Related
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk

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