CyberHunter
Local dataset, no network
// Other services

Port 3333: DEC Notes

Port 3333 is assigned by IANA to dec-notes (DEC Notes).

3333

How dec-notes works

Other services
client:3333dec-notesresponse client:3333dec-notesresponse

The client sends a request to port 3333 and the dec-notes 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
Other services
01 Security

Is port 3333 dangerous?

We have no specific security note for port 3333. 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 3333

ServicePortTransportDescriptionReferenceUpdated
dec-notes 3333 TCP, UDP DEC Notes - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3333, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3333'      # process listening on 3333
sudo lsof -nP -i :3333

macOS

sudo lsof -nP -i :3333

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3333 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3333
netstat -ano | findstr :3333

From another machine

nmap -p 3333 -sV <host>
sudo nmap -sU -p 3333 <host>
nc -zv <host> 3333

Block it in the firewall

sudo ufw deny 3333/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3333" -Direction Inbound -LocalPort 3333 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3333 used for?

Port 3333 is assigned by IANA to dec-notes (DEC Notes).

Is port 3333 TCP or UDP?

Port 3333 is registered for TCP and UDP.

Is it safe to open port 3333?

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 3333 is open?

On Linux run "ss -ltnup 'sport = :3333'", on macOS "lsof -nP -i :3333", and on Windows "netstat -ano | findstr :3333" to see the local process. From another machine, "nmap -p 3333 <host>" shows whether it is reachable.

05 Related
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