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// Other services

Port 16789: This server provides callable services to mainframe External Security Managers from any TCP/IP platform

Port 16789 is assigned by IANA to cadsisvr (This server provides callable services to mainframe External Security Managers from any TCP/IP platform).

16789

How cadsisvr works

Other services
client:16789cadsisvrresponse client:16789cadsisvrresponse

The client sends a request to port 16789 and the cadsisvr service answers.

Transport
TCP
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 16789 dangerous?

We have no specific security note for port 16789. 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 16789

ServicePortTransportDescriptionReferenceUpdated
cadsisvr 16789 TCP This server provides callable services to mainframe External Security Managers from any TCP/IP platform - 2023-03-29
-16789-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 16789, and is it reachable?

Linux

sudo ss -ltnup 'sport = :16789'      # process listening on 16789
sudo lsof -nP -i :16789

macOS

sudo lsof -nP -i :16789

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 16789 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 16789
netstat -ano | findstr :16789

From another machine

nmap -p 16789 -sV <host>
nc -zv <host> 16789

Block it in the firewall

sudo ufw deny 16789/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 16789" -Direction Inbound -LocalPort 16789 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 16789 used for?

Port 16789 is assigned by IANA to cadsisvr (This server provides callable services to mainframe External Security Managers from any TCP/IP platform).

Is port 16789 TCP or UDP?

Port 16789 is registered for TCP.

Is it safe to open port 16789?

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 16789 is open?

On Linux run "ss -ltnup 'sport = :16789'", on macOS "lsof -nP -i :16789", and on Windows "netstat -ano | findstr :16789" to see the local process. From another machine, "nmap -p 16789 <host>" shows whether it is reachable.

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