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// Other services

Port 3251: Sys Scanner

Port 3251 is assigned by IANA to sysscanner (Sys Scanner).

3251

How sysscanner works

Other services
client:3251sysscannerresponse client:3251sysscannerresponse

The client sends a request to port 3251 and the sysscanner 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 3251 dangerous?

We have no specific security note for port 3251. 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 3251

ServicePortTransportDescriptionReferenceUpdated
sysscanner 3251 TCP, UDP Sys Scanner - 2002-02

// source: IANA service name and port number registry

03 Check it

Which program uses port 3251, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3251'      # process listening on 3251
sudo lsof -nP -i :3251

macOS

sudo lsof -nP -i :3251

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3251 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3251
netstat -ano | findstr :3251

From another machine

nmap -p 3251 -sV <host>
sudo nmap -sU -p 3251 <host>
nc -zv <host> 3251

Block it in the firewall

sudo ufw deny 3251/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3251" -Direction Inbound -LocalPort 3251 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3251 used for?

Port 3251 is assigned by IANA to sysscanner (Sys Scanner).

Is port 3251 TCP or UDP?

Port 3251 is registered for TCP and UDP.

Is it safe to open port 3251?

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 3251 is open?

On Linux run "ss -ltnup 'sport = :3251'", on macOS "lsof -nP -i :3251", and on Windows "netstat -ano | findstr :3251" to see the local process. From another machine, "nmap -p 3251 <host>" shows whether it is reachable.

05 Related
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