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Registered port (1024–10000) Standard/Low risk

Port 3938 DBCONTROL-AGENT

Quick answer

Port 3938 is the IANA-assigned dbcontrol-agent port for Oracle dbControl Agent po IANA assigned this well-formed service name as a replacement for "dbcontrol_agent" (TCP / UDP).

Check and block Is it safe? Troubleshooting FAQ
TransportTCP / UDP
RiskStandard/Low
Typical useDatabases

What is port 3938 used for?

Port 3938 is assigned to dbcontrol-agent and uses TCP / UDP. The IANA registry describes the service as “Oracle dbControl Agent po IANA assigned this well-formed service name as a replacement for "dbcontrol_agent".”. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once. The same port is also registered under dbcontrol_agent.

Ports are the transport-layer address a service listens on. A client that wants to reach dbcontrol-agent connects to port 3938. A TCP connection is refused when nothing is listening, while a UDP request simply goes unanswered. That is why a port conflict appears whenever two processes try to bind the same number.

Use the commands below to confirm whether port 3938 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.

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Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Todd_Guay].

Check and block port 3938

Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.

Check on Linux

sudo ss -tlpn 'sport = :3938' sudo ss -ulpn 'sport = :3938'

Check on Windows

Get-NetTCPConnection -LocalPort 3938 -State Listen -ErrorAction SilentlyContinue Get-NetUDPEndpoint -LocalPort 3938 -ErrorAction SilentlyContinue

Block with UFW

sudo ufw deny 3938/tcp sudo ufw deny 3938/udp

Block with iptables

sudo iptables -A INPUT -p tcp --dport 3938 -j DROP sudo iptables -A INPUT -p udp --dport 3938 -j DROP

These commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.

Is port 3938 safe to expose?

Standard/Low

This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.

Where port 3938 is usually used

Most traffic on port 3938 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.

Demo

Open a test connection

Probe the TCP listener before you debug credentials or driver settings.

nc -vz 127.0.0.1 3938

Common problems with port 3938

Connection refused or timed out

Refused usually means the host is reachable but nothing is listening on port 3938. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.

Port already in use

Find the process holding the port with sudo ss -tlpn 'sport = :3938' or sudo lsof -i :3938. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.

Firewall rule did not survive a reboot

UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.

The port is blocked but still reachable

A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.

Port 3938 at a glance

Port number3938
Service namedbcontrol-agent
Aliasesdbcontrol_agent
Transport protocolTCP / UDP
CategoryDatabases
RangeRegistered port (1024–10000)
Risk levelStandard/Low
Registered assignee[Todd_Guay]
Registry descriptionOracle dbControl Agent po IANA assigned this well-formed service name as a replacement for "dbcontrol_agent".
SourceIANA Service Name and Transport Protocol Port Number Registry

Frequently asked questions

What is port 3938 used for?

Port 3938 (DBCONTROL-AGENT) uses TCP / UDP. Oracle dbControl Agent po IANA assigned this well-formed service name as a replacement for "dbcontrol_agent".

How do I check if port 3938 is open?

On Linux run `sudo ss -tlpn 'sport = :3938'` and `sudo ss -ulpn 'sport = :3938'`. On Windows run `Get-NetTCPConnection -LocalPort 3938 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 3938 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 3938; empty output usually means nothing is bound to it.

How do I block port 3938?

With UFW run `sudo ufw deny 3938/tcp` and `sudo ufw deny 3938/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 3938 -j DROP` and `sudo iptables -A INPUT -p udp --dport 3938 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.

Is port 3938 safe to expose?

This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.

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Primary data: IANA Service Name and Transport Protocol Port Number Registry.

Last reviewed 2026-10-30 · Methodology · About · Privacy