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// Other services

Port 25901: NIObserver

Port 25901 is assigned by IANA to niobserver (NIObserver).

25901

How niobserver works

Other services
client:25901niobserverresponse client:25901niobserverresponse

The client sends a request to port 25901 and the niobserver 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 25901 dangerous?

We have no specific security note for port 25901. 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 25901

ServicePortTransportDescriptionReferenceUpdated
niobserver 25901 TCP, UDP NIObserver - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 25901, and is it reachable?

Linux

sudo ss -ltnup 'sport = :25901'      # process listening on 25901
sudo lsof -nP -i :25901

macOS

sudo lsof -nP -i :25901

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 25901 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 25901
netstat -ano | findstr :25901

From another machine

nmap -p 25901 -sV <host>
sudo nmap -sU -p 25901 <host>
nc -zv <host> 25901

Block it in the firewall

sudo ufw deny 25901/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 25901" -Direction Inbound -LocalPort 25901 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 25901 used for?

Port 25901 is assigned by IANA to niobserver (NIObserver).

Is port 25901 TCP or UDP?

Port 25901 is registered for TCP and UDP.

Is it safe to open port 25901?

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 25901 is open?

On Linux run "ss -ltnup 'sport = :25901'", on macOS "lsof -nP -i :25901", and on Windows "netstat -ano | findstr :25901" to see the local process. From another machine, "nmap -p 25901 <host>" shows whether it is reachable.

05 Related
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