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// Network services

Port 4309: Exsequi Appliance Discovery

Port 4309 is assigned by IANA to dserver (Exsequi Appliance Discovery).

4309

How dserver works

Network services
client:4309dserverresponse client:4309dserverresponse

The client sends a request to port 4309 and the dserver service answers.

Transport
TCP · 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 4309 dangerous?

We have no specific security note for port 4309. 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 4309

ServicePortTransportDescriptionReferenceUpdated
dserver 4309 TCP, UDP Exsequi Appliance Discovery - 2007-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 4309, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4309'      # process listening on 4309
sudo lsof -nP -i :4309

macOS

sudo lsof -nP -i :4309

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4309 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4309
netstat -ano | findstr :4309

From another machine

nmap -p 4309 -sV <host>
sudo nmap -sU -p 4309 <host>
nc -zv <host> 4309

Block it in the firewall

sudo ufw deny 4309/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4309" -Direction Inbound -LocalPort 4309 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4309 used for?

Port 4309 is assigned by IANA to dserver (Exsequi Appliance Discovery).

Is port 4309 TCP or UDP?

Port 4309 is registered for TCP and UDP.

Is it safe to open port 4309?

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 4309 is open?

On Linux run "ss -ltnup 'sport = :4309'", on macOS "lsof -nP -i :4309", and on Windows "netstat -ano | findstr :4309" to see the local process. From another machine, "nmap -p 4309 <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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