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// Other services

Port 2728: SQDR

Port 2728 is assigned by IANA to sqdr (SQDR).

2728

How sqdr works

Other services
client:2728sqdrresponse client:2728sqdrresponse

The client sends a request to port 2728 and the sqdr 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 2728 dangerous?

We have no specific security note for port 2728. 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 2728

ServicePortTransportDescriptionReferenceUpdated
sqdr 2728 TCP, UDP SQDR - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 2728, and is it reachable?

Linux

sudo ss -ltnup 'sport = :2728'      # process listening on 2728
sudo lsof -nP -i :2728

macOS

sudo lsof -nP -i :2728

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 2728 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 2728
netstat -ano | findstr :2728

From another machine

nmap -p 2728 -sV <host>
sudo nmap -sU -p 2728 <host>
nc -zv <host> 2728

Block it in the firewall

sudo ufw deny 2728/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 2728" -Direction Inbound -LocalPort 2728 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 2728 used for?

Port 2728 is assigned by IANA to sqdr (SQDR).

Is port 2728 TCP or UDP?

Port 2728 is registered for TCP and UDP.

Is it safe to open port 2728?

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 2728 is open?

On Linux run "ss -ltnup 'sport = :2728'", on macOS "lsof -nP -i :2728", and on Windows "netstat -ano | findstr :2728" to see the local process. From another machine, "nmap -p 2728 <host>" shows whether it is reachable.

05 Related
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