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// Other services

Port 558: SDNSKMP

Port 558 is assigned by IANA to sdnskmp (SDNSKMP).

558

How sdnskmp works

Other services
client:558sdnskmpresponse client:558sdnskmpresponse

The client sends a request to port 558 and the sdnskmp 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 558 dangerous?

We have no specific security note for port 558. 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 558

ServicePortTransportDescriptionReferenceUpdated
sdnskmp 558 TCP, UDP SDNSKMP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 558, and is it reachable?

Linux

sudo ss -ltnup 'sport = :558'      # process listening on 558
sudo lsof -nP -i :558

macOS

sudo lsof -nP -i :558

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 558 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 558
netstat -ano | findstr :558

From another machine

nmap -p 558 -sV <host>
sudo nmap -sU -p 558 <host>
nc -zv <host> 558

Block it in the firewall

sudo ufw deny 558/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 558" -Direction Inbound -LocalPort 558 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 558 used for?

Port 558 is assigned by IANA to sdnskmp (SDNSKMP).

Is port 558 TCP or UDP?

Port 558 is registered for TCP and UDP.

Is it safe to open port 558?

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 558 is open?

On Linux run "ss -ltnup 'sport = :558'", on macOS "lsof -nP -i :558", and on Windows "netstat -ano | findstr :558" to see the local process. From another machine, "nmap -p 558 <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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