CyberHunter
Local dataset, no network
// Other services

Port 516: videotex

Port 516 is assigned by IANA to videotex (videotex).

516

How videotex works

Other services
client:516videotexresponse client:516videotexresponse

The client sends a request to port 516 and the videotex 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 516 dangerous?

We have no specific security note for port 516. 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 516

ServicePortTransportDescriptionReferenceUpdated
videotex 516 TCP, UDP videotex - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 516, and is it reachable?

Linux

sudo ss -ltnup 'sport = :516'      # process listening on 516
sudo lsof -nP -i :516

macOS

sudo lsof -nP -i :516

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 516 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 516
netstat -ano | findstr :516

From another machine

nmap -p 516 -sV <host>
sudo nmap -sU -p 516 <host>
nc -zv <host> 516

Block it in the firewall

sudo ufw deny 516/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 516" -Direction Inbound -LocalPort 516 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 516 used for?

Port 516 is assigned by IANA to videotex (videotex).

Is port 516 TCP or UDP?

Port 516 is registered for TCP and UDP.

Is it safe to open port 516?

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 516 is open?

On Linux run "ss -ltnup 'sport = :516'", on macOS "lsof -nP -i :516", and on Windows "netstat -ano | findstr :516" to see the local process. From another machine, "nmap -p 516 <host>" shows whether it is reachable.

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