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// Databases & caches

Port 3891: Oracle RTC-PM port

Port 3891 is assigned by IANA to rtc-pm-port (Oracle RTC-PM port).

3891

How rtc-pm-port works

Databases & caches
app:3891rtc-pm-port app:3891rtc-pm-port

The application sends a SQL query to the rtc-pm-port server on port 3891, which returns rows from its tables.

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
Databases & caches
01 Security

Is port 3891 dangerous?

We have no specific security note for port 3891. Its risk depends on the program actually listening on it. General advice for databases & caches services:

  • Bind the service to localhost or a private network, never to a public address.
  • Enable authentication, use per-application accounts and require TLS.
  • Watch for exposed Docker ports: publish them on 127.0.0.1 only.
02 Registry

IANA registry entries for port 3891

ServicePortTransportDescriptionReferenceUpdated
rtc-pm-port 3891 TCP, UDP Oracle RTC-PM port - 2003-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 3891, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3891'      # process listening on 3891
sudo lsof -nP -i :3891

macOS

sudo lsof -nP -i :3891

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3891 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3891
netstat -ano | findstr :3891

From another machine

nmap -p 3891 -sV <host>
sudo nmap -sU -p 3891 <host>
nc -zv <host> 3891

Block it in the firewall

sudo ufw deny 3891/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3891" -Direction Inbound -LocalPort 3891 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3891 used for?

Port 3891 is assigned by IANA to rtc-pm-port (Oracle RTC-PM port).

Is port 3891 TCP or UDP?

Port 3891 is registered for TCP and UDP.

Is it safe to open port 3891?

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. Bind the service to localhost or a private network, never to a public address.

How do I check if port 3891 is open?

On Linux run "ss -ltnup 'sport = :3891'", on macOS "lsof -nP -i :3891", and on Windows "netstat -ano | findstr :3891" to see the local process. From another machine, "nmap -p 3891 <host>" shows whether it is reachable.

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