CyberHunter
Local dataset, no network
// Other services

Port 4086: Firewall/NAT state table synchronization

Port 4086 is assigned by IANA to ftsync (Firewall/NAT state table synchronization).

4086

How ftsync works

Other services
client:4086ftsyncresponse client:4086ftsyncresponse

The client sends a request to port 4086 and the ftsync 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
Other services
01 Security

Is port 4086 dangerous?

We have no specific security note for port 4086. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 4086

ServicePortTransportDescriptionReferenceUpdated
ftsync 4086 UDP Firewall/NAT state table synchronization - 2008-06-06
-4086-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 4086, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4086'      # process listening on 4086
sudo lsof -nP -i :4086

macOS

sudo lsof -nP -i :4086

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4086 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4086
netstat -ano | findstr :4086

From another machine

nmap -p 4086 -sV <host>
sudo nmap -sU -p 4086 <host>
nc -zv <host> 4086

Block it in the firewall

sudo ufw deny 4086/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4086" -Direction Inbound -LocalPort 4086 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 4086 used for?

Port 4086 is assigned by IANA to ftsync (Firewall/NAT state table synchronization).

Is port 4086 TCP or UDP?

Port 4086 is registered for UDP.

Is it safe to open port 4086?

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. Close the port if nothing on the host needs it.

How do I check if port 4086 is open?

On Linux run "ss -ltnup 'sport = :4086'", on macOS "lsof -nP -i :4086", and on Windows "netstat -ano | findstr :4086" to see the local process. From another machine, "nmap -p 4086 <host>" shows whether it is reachable.

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