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// Other services

Port 33331: DiamondCentral Interface

Port 33331 is assigned by IANA to diamondport (DiamondCentral Interface).

33331

How diamondport works

Other services
client:33331diamondportresponse client:33331diamondportresponse

The client sends a request to port 33331 and the diamondport 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 33331 dangerous?

We have no specific security note for port 33331. 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 33331

ServicePortTransportDescriptionReferenceUpdated
diamondport 33331 TCP, UDP DiamondCentral Interface - 2002-07

// source: IANA service name and port number registry

03 Check it

Which program uses port 33331, and is it reachable?

Linux

sudo ss -ltnup 'sport = :33331'      # process listening on 33331
sudo lsof -nP -i :33331

macOS

sudo lsof -nP -i :33331

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 33331 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 33331
netstat -ano | findstr :33331

From another machine

nmap -p 33331 -sV <host>
sudo nmap -sU -p 33331 <host>
nc -zv <host> 33331

Block it in the firewall

sudo ufw deny 33331/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 33331" -Direction Inbound -LocalPort 33331 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 33331 used for?

Port 33331 is assigned by IANA to diamondport (DiamondCentral Interface).

Is port 33331 TCP or UDP?

Port 33331 is registered for TCP and UDP.

Is it safe to open port 33331?

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 33331 is open?

On Linux run "ss -ltnup 'sport = :33331'", on macOS "lsof -nP -i :33331", and on Windows "netstat -ano | findstr :33331" to see the local process. From another machine, "nmap -p 33331 <host>" shows whether it is reachable.

05 Related
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