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// Other services

Port 621: ESCP

Port 621 is assigned by IANA to escp-ip (ESCP).

621

How escp-ip works

Other services
client:621escp-ipresponse client:621escp-ipresponse

The client sends a request to port 621 and the escp-ip 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
Well-known (0-1023)
Category
Other services
01 Security

Is port 621 dangerous?

We have no specific security note for port 621. 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 621

ServicePortTransportDescriptionReferenceUpdated
escp-ip 621 TCP, UDP ESCP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 621, and is it reachable?

Linux

sudo ss -ltnup 'sport = :621'      # process listening on 621
sudo lsof -nP -i :621

macOS

sudo lsof -nP -i :621

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 621 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 621
netstat -ano | findstr :621

From another machine

nmap -p 621 -sV <host>
sudo nmap -sU -p 621 <host>
nc -zv <host> 621

Block it in the firewall

sudo ufw deny 621/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 621" -Direction Inbound -LocalPort 621 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 621 used for?

Port 621 is assigned by IANA to escp-ip (ESCP).

Is port 621 TCP or UDP?

Port 621 is registered for TCP and UDP.

Is it safe to open port 621?

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 621 is open?

On Linux run "ss -ltnup 'sport = :621'", on macOS "lsof -nP -i :621", and on Windows "netstat -ano | findstr :621" to see the local process. From another machine, "nmap -p 621 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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