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// Other services

Port 28001: PQ Service

Port 28001 is assigned by IANA to pqsp (PQ Service).

28001

How pqsp works

Other services
client:28001pqspresponse client:28001pqspresponse

The client sends a request to port 28001 and the pqsp service answers.

Transport
TCP
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 28001 dangerous?

We have no specific security note for port 28001. 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 28001

ServicePortTransportDescriptionReferenceUpdated
pqsp 28001 TCP PQ Service - 2009-09-15
-28001-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 28001, and is it reachable?

Linux

sudo ss -ltnup 'sport = :28001'      # process listening on 28001
sudo lsof -nP -i :28001

macOS

sudo lsof -nP -i :28001

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 28001 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 28001
netstat -ano | findstr :28001

From another machine

nmap -p 28001 -sV <host>
nc -zv <host> 28001

Block it in the firewall

sudo ufw deny 28001/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 28001" -Direction Inbound -LocalPort 28001 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 28001 used for?

Port 28001 is assigned by IANA to pqsp (PQ Service).

Is port 28001 TCP or UDP?

Port 28001 is registered for TCP.

Is it safe to open port 28001?

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 28001 is open?

On Linux run "ss -ltnup 'sport = :28001'", on macOS "lsof -nP -i :28001", and on Windows "netstat -ano | findstr :28001" to see the local process. From another machine, "nmap -p 28001 <host>" shows whether it is reachable.

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