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// Other services

Port 4045: Network Paging Protocol

Port 4045 is assigned by IANA to npp (Network Paging Protocol).

4045

How npp works

Other services
client:4045nppresponse client:4045nppresponse

The client sends a request to port 4045 and the npp 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 4045 dangerous?

We have no specific security note for port 4045. 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 4045

ServicePortTransportDescriptionReferenceUpdated
npp 4045 TCP, UDP Network Paging Protocol
Reported: Known UNAUTHORIZED USE: Port 4045
 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 4045, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4045'      # process listening on 4045
sudo lsof -nP -i :4045

macOS

sudo lsof -nP -i :4045

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4045 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4045
netstat -ano | findstr :4045

From another machine

nmap -p 4045 -sV <host>
sudo nmap -sU -p 4045 <host>
nc -zv <host> 4045

Block it in the firewall

sudo ufw deny 4045/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4045" -Direction Inbound -LocalPort 4045 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4045 used for?

Port 4045 is assigned by IANA to npp (Network Paging Protocol).

Is port 4045 TCP or UDP?

Port 4045 is registered for TCP and UDP.

Is it safe to open port 4045?

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 4045 is open?

On Linux run "ss -ltnup 'sport = :4045'", on macOS "lsof -nP -i :4045", and on Windows "netstat -ano | findstr :4045" to see the local process. From another machine, "nmap -p 4045 <host>" shows whether it is reachable.

05 Related
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