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// Other services

Port 503: Intrinsa

Port 503 is assigned by IANA to intrinsa (Intrinsa).

503

How intrinsa works

Other services
client:503intrinsaresponse client:503intrinsaresponse

The client sends a request to port 503 and the intrinsa 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 503 dangerous?

We have no specific security note for port 503. 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 503

ServicePortTransportDescriptionReferenceUpdated
intrinsa 503 TCP, UDP Intrinsa - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 503, and is it reachable?

Linux

sudo ss -ltnup 'sport = :503'      # process listening on 503
sudo lsof -nP -i :503

macOS

sudo lsof -nP -i :503

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 503 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 503
netstat -ano | findstr :503

From another machine

nmap -p 503 -sV <host>
sudo nmap -sU -p 503 <host>
nc -zv <host> 503

Block it in the firewall

sudo ufw deny 503/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 503" -Direction Inbound -LocalPort 503 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 503 used for?

Port 503 is assigned by IANA to intrinsa (Intrinsa).

Is port 503 TCP or UDP?

Port 503 is registered for TCP and UDP.

Is it safe to open port 503?

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 503 is open?

On Linux run "ss -ltnup 'sport = :503'", on macOS "lsof -nP -i :503", and on Windows "netstat -ano | findstr :503" to see the local process. From another machine, "nmap -p 503 <host>" shows whether it is reachable.

05 Related
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