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// Other services

Port 4333: ArrowHead Service Protocol (AHSP)

Port 4333 is assigned by IANA to ahsp (ArrowHead Service Protocol (AHSP)).

4333

How ahsp works

Other services
client:4333ahspresponse client:4333ahspresponse

The client sends a request to port 4333 and the ahsp service answers.

Transport
TCP · UDP · SCTP
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 4333 dangerous?

We have no specific security note for port 4333. 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 4333

ServicePortTransportDescriptionReferenceUpdated
ahsp 4333 TCP, UDP, SCTP ArrowHead Service Protocol (AHSP) - 2014-04-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 4333, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4333'      # process listening on 4333
sudo lsof -nP -i :4333

macOS

sudo lsof -nP -i :4333

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4333 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4333
netstat -ano | findstr :4333

From another machine

nmap -p 4333 -sV <host>
sudo nmap -sU -p 4333 <host>
nc -zv <host> 4333

Block it in the firewall

sudo ufw deny 4333/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4333" -Direction Inbound -LocalPort 4333 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4333 used for?

Port 4333 is assigned by IANA to ahsp (ArrowHead Service Protocol (AHSP)).

Is port 4333 TCP or UDP?

Port 4333 is registered for TCP and UDP and SCTP.

Is it safe to open port 4333?

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 4333 is open?

On Linux run "ss -ltnup 'sport = :4333'", on macOS "lsof -nP -i :4333", and on Windows "netstat -ano | findstr :4333" to see the local process. From another machine, "nmap -p 4333 <host>" shows whether it is reachable.

05 Related
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