CyberHunter
Local dataset, no network
// Other services

Port 2021:

Port 2021 is assigned by IANA to servexec (), xinuexpansion1 ().

2021

How servexec works

Other services
client:2021servexecresponse client:2021servexecresponse

The client sends a request to port 2021 and the servexec service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 2021 dangerous?

We have no specific security note for port 2021. 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 2021

ServicePortTransportDescriptionReferenceUpdated
servexec 2021 TCP - -
xinuexpansion1 2021 UDP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 2021, and is it reachable?

Linux

sudo ss -ltnup 'sport = :2021'      # process listening on 2021
sudo lsof -nP -i :2021

macOS

sudo lsof -nP -i :2021

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 2021 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 2021
netstat -ano | findstr :2021

From another machine

nmap -p 2021 -sV <host>
sudo nmap -sU -p 2021 <host>
nc -zv <host> 2021

Block it in the firewall

sudo ufw deny 2021/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 2021" -Direction Inbound -LocalPort 2021 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 2021 used for?

Port 2021 is assigned by IANA to servexec (), xinuexpansion1 ().

Is port 2021 TCP or UDP?

Port 2021 is registered for TCP and UDP.

Is it safe to open port 2021?

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 2021 is open?

On Linux run "ss -ltnup 'sport = :2021'", on macOS "lsof -nP -i :2021", and on Windows "netstat -ano | findstr :2021" to see the local process. From another machine, "nmap -p 2021 <host>" shows whether it is reachable.

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