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// Other services

Port 5281: Undo License Manager

Port 5281 is assigned by IANA to undo-lm (Undo License Manager).

5281

How undo-lm works

Other services
client:5281undo-lmresponse client:5281undo-lmresponse

The client sends a request to port 5281 and the undo-lm 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 5281 dangerous?

We have no specific security note for port 5281. 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 5281

ServicePortTransportDescriptionReferenceUpdated
undo-lm 5281 TCP Undo License Manager - 2019-01-25
-5281-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 5281, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5281'      # process listening on 5281
sudo lsof -nP -i :5281

macOS

sudo lsof -nP -i :5281

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5281 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5281
netstat -ano | findstr :5281

From another machine

nmap -p 5281 -sV <host>
nc -zv <host> 5281

Block it in the firewall

sudo ufw deny 5281/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5281" -Direction Inbound -LocalPort 5281 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5281 used for?

Port 5281 is assigned by IANA to undo-lm (Undo License Manager).

Is port 5281 TCP or UDP?

Port 5281 is registered for TCP.

Is it safe to open port 5281?

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 5281 is open?

On Linux run "ss -ltnup 'sport = :5281'", on macOS "lsof -nP -i :5281", and on Windows "netstat -ano | findstr :5281" to see the local process. From another machine, "nmap -p 5281 <host>" shows whether it is reachable.

05 Related
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