CyberHunter
Local dataset, no network
// Other services

Port 2781: whosells

Port 2781 is assigned by IANA to whosells (whosells).

2781

How whosells works

Other services
client:2781whosellsresponse client:2781whosellsresponse

The client sends a request to port 2781 and the whosells 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 2781 dangerous?

We have no specific security note for port 2781. 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 2781

ServicePortTransportDescriptionReferenceUpdated
whosells 2781 TCP, UDP whosells - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 2781, and is it reachable?

Linux

sudo ss -ltnup 'sport = :2781'      # process listening on 2781
sudo lsof -nP -i :2781

macOS

sudo lsof -nP -i :2781

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 2781 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 2781
netstat -ano | findstr :2781

From another machine

nmap -p 2781 -sV <host>
sudo nmap -sU -p 2781 <host>
nc -zv <host> 2781

Block it in the firewall

sudo ufw deny 2781/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 2781" -Direction Inbound -LocalPort 2781 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 2781 used for?

Port 2781 is assigned by IANA to whosells (whosells).

Is port 2781 TCP or UDP?

Port 2781 is registered for TCP and UDP.

Is it safe to open port 2781?

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 2781 is open?

On Linux run "ss -ltnup 'sport = :2781'", on macOS "lsof -nP -i :2781", and on Windows "netstat -ano | findstr :2781" to see the local process. From another machine, "nmap -p 2781 <host>" shows whether it is reachable.

05 Related
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