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// Other services

Port 420: SMPTE

Port 420 is assigned by IANA to smpte (SMPTE).

420

How smpte works

Other services
client:420smpteresponse client:420smpteresponse

The client sends a request to port 420 and the smpte 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 420 dangerous?

We have no specific security note for port 420. 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 420

ServicePortTransportDescriptionReferenceUpdated
smpte 420 TCP, UDP SMPTE - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 420, and is it reachable?

Linux

sudo ss -ltnup 'sport = :420'      # process listening on 420
sudo lsof -nP -i :420

macOS

sudo lsof -nP -i :420

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 420 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 420
netstat -ano | findstr :420

From another machine

nmap -p 420 -sV <host>
sudo nmap -sU -p 420 <host>
nc -zv <host> 420

Block it in the firewall

sudo ufw deny 420/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 420" -Direction Inbound -LocalPort 420 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 420 used for?

Port 420 is assigned by IANA to smpte (SMPTE).

Is port 420 TCP or UDP?

Port 420 is registered for TCP and UDP.

Is it safe to open port 420?

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 420 is open?

On Linux run "ss -ltnup 'sport = :420'", on macOS "lsof -nP -i :420", and on Windows "netstat -ano | findstr :420" to see the local process. From another machine, "nmap -p 420 <host>" shows whether it is reachable.

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