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// Other services

Port 3621: EPSON Network Screen Port

Port 3621 is assigned by IANA to ep-nsp (EPSON Network Screen Port).

3621

How ep-nsp works

Other services
client:3621ep-nspresponse client:3621ep-nspresponse

The client sends a request to port 3621 and the ep-nsp 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 3621 dangerous?

We have no specific security note for port 3621. 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 3621

ServicePortTransportDescriptionReferenceUpdated
ep-nsp 3621 TCP, UDP EPSON Network Screen Port - 2002-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 3621, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3621'      # process listening on 3621
sudo lsof -nP -i :3621

macOS

sudo lsof -nP -i :3621

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3621 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3621
netstat -ano | findstr :3621

From another machine

nmap -p 3621 -sV <host>
sudo nmap -sU -p 3621 <host>
nc -zv <host> 3621

Block it in the firewall

sudo ufw deny 3621/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3621" -Direction Inbound -LocalPort 3621 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3621 used for?

Port 3621 is assigned by IANA to ep-nsp (EPSON Network Screen Port).

Is port 3621 TCP or UDP?

Port 3621 is registered for TCP and UDP.

Is it safe to open port 3621?

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 3621 is open?

On Linux run "ss -ltnup 'sport = :3621'", on macOS "lsof -nP -i :3621", and on Windows "netstat -ano | findstr :3621" to see the local process. From another machine, "nmap -p 3621 <host>" shows whether it is reachable.

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