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Local dataset, no network
// Other services

Port 12003: IBM Enterprise Extender SNA COS Medium Priority

Port 12003 is assigned by IANA to entextmed (IBM Enterprise Extender SNA COS Medium Priority).

12003

How entextmed works

Other services
client:12003entextmedresponse client:12003entextmedresponse

The client sends a request to port 12003 and the entextmed 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 12003 dangerous?

We have no specific security note for port 12003. 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 12003

ServicePortTransportDescriptionReferenceUpdated
entextmed 12003 TCP, UDP IBM Enterprise Extender SNA COS Medium Priority - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 12003, and is it reachable?

Linux

sudo ss -ltnup 'sport = :12003'      # process listening on 12003
sudo lsof -nP -i :12003

macOS

sudo lsof -nP -i :12003

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 12003 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 12003
netstat -ano | findstr :12003

From another machine

nmap -p 12003 -sV <host>
sudo nmap -sU -p 12003 <host>
nc -zv <host> 12003

Block it in the firewall

sudo ufw deny 12003/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 12003" -Direction Inbound -LocalPort 12003 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 12003 used for?

Port 12003 is assigned by IANA to entextmed (IBM Enterprise Extender SNA COS Medium Priority).

Is port 12003 TCP or UDP?

Port 12003 is registered for TCP and UDP.

Is it safe to open port 12003?

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 12003 is open?

On Linux run "ss -ltnup 'sport = :12003'", on macOS "lsof -nP -i :12003", and on Windows "netstat -ano | findstr :12003" to see the local process. From another machine, "nmap -p 12003 <host>" shows whether it is reachable.

05 Related
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