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// Other services

Port 555:

Port 555 is assigned by IANA to dsf ().

555

How dsf works

Other services
client:555dsfresponse client:555dsfresponse

The client sends a request to port 555 and the dsf 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 555 dangerous?

We have no specific security note for port 555. 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 555

ServicePortTransportDescriptionReferenceUpdated
dsf 555 TCP, UDP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 555, and is it reachable?

Linux

sudo ss -ltnup 'sport = :555'      # process listening on 555
sudo lsof -nP -i :555

macOS

sudo lsof -nP -i :555

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 555 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 555
netstat -ano | findstr :555

From another machine

nmap -p 555 -sV <host>
sudo nmap -sU -p 555 <host>
nc -zv <host> 555

Block it in the firewall

sudo ufw deny 555/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 555" -Direction Inbound -LocalPort 555 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 555 used for?

Port 555 is assigned by IANA to dsf ().

Is port 555 TCP or UDP?

Port 555 is registered for TCP and UDP.

Is it safe to open port 555?

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 555 is open?

On Linux run "ss -ltnup 'sport = :555'", on macOS "lsof -nP -i :555", and on Windows "netstat -ano | findstr :555" to see the local process. From another machine, "nmap -p 555 <host>" shows whether it is reachable.

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