Port 1813 RADIUS-ACCT
Port 1813 is the IANA-assigned radius-acct port for RADIUS Accounting (TCP / UDP).
What is port 1813 used for?
Port 1813 is assigned to radius-acct and uses TCP / UDP. The IANA registry describes the service as “RADIUS Accounting”. 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.
Ports are the transport-layer address a service listens on. A client that wants to reach radius-acct connects to port 1813. 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 1813 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.
Browse all Authentication and access ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Reference: [RFC 2866].
Check and block port 1813
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 = :1813'
sudo ss -ulpn 'sport = :1813'Check on Windows
Get-NetTCPConnection -LocalPort 1813 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 1813 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 1813/tcp
sudo ufw deny 1813/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 1813 -j DROP
sudo iptables -A INPUT -p udp --dport 1813 -j DROPThese 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 1813 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. 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 1813 is usually used
Most traffic on port 1813 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Network devices authenticating users through a central service.
- Wi-Fi, VPN and remote-access gateways enforcing access policy.
- Accounting and session logs used for audits.
Send a RADIUS accounting record
RADIUS accounting normally uses UDP 1813. This sends a single Start record with a test secret.
echo "User-Name=alice,Acct-Status-Type=Start" | radclient -x 127.0.0.1:1813 acct testing123Common problems with port 1813
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 1813. 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 = :1813' or sudo lsof -i :1813. 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 1813 at a glance
| Port number | 1813 |
|---|---|
| Service name | radius-acct |
| Transport protocol | TCP / UDP |
| Category | Authentication and access |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Registered assignee | Not listed |
| Reference | [RFC 2866] |
| Registry description | RADIUS Accounting |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 1813 used for?
Port 1813 (RADIUS-ACCT) uses TCP / UDP. RADIUS Accounting.
How do I check if port 1813 is open?
On Linux run `sudo ss -tlpn 'sport = :1813'` and `sudo ss -ulpn 'sport = :1813'`. On Windows run `Get-NetTCPConnection -LocalPort 1813 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 1813 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 1813; empty output usually means nothing is bound to it.
How do I block port 1813?
With UFW run `sudo ufw deny 1813/tcp` and `sudo ufw deny 1813/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 1813 -j DROP` and `sudo iptables -A INPUT -p udp --dport 1813 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 1813 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.
Related ports
- Port 1812 · radiusRADIUS
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- Port 2478 · ssm-csspsSecurSight Authentication Server (SSL)
- Port 750 · kerberos-ivkerberos version iv
- Port 2821 · vrts-at-portVERITAS Authentication Service
- Port 749 · kerberos-admkerberos administration
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy