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// Other services

Port 5421: Net Support 2

Port 5421 is assigned by IANA to netsupport2 (Net Support 2).

5421

How netsupport2 works

Other services
client:5421netsupport2response client:5421netsupport2response

The client sends a request to port 5421 and the netsupport2 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 5421 dangerous?

We have no specific security note for port 5421. 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 5421

ServicePortTransportDescriptionReferenceUpdated
netsupport2 5421 TCP, UDP Net Support 2 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 5421, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5421'      # process listening on 5421
sudo lsof -nP -i :5421

macOS

sudo lsof -nP -i :5421

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5421 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5421
netstat -ano | findstr :5421

From another machine

nmap -p 5421 -sV <host>
sudo nmap -sU -p 5421 <host>
nc -zv <host> 5421

Block it in the firewall

sudo ufw deny 5421/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5421" -Direction Inbound -LocalPort 5421 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5421 used for?

Port 5421 is assigned by IANA to netsupport2 (Net Support 2).

Is port 5421 TCP or UDP?

Port 5421 is registered for TCP and UDP.

Is it safe to open port 5421?

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 5421 is open?

On Linux run "ss -ltnup 'sport = :5421'", on macOS "lsof -nP -i :5421", and on Windows "netstat -ano | findstr :5421" to see the local process. From another machine, "nmap -p 5421 <host>" shows whether it is reachable.

05 Related
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