Port 9306 SPHINXQL
Port 9306 is the IANA-assigned sphinxql port for Sphinx search server (MySQL listener) (TCP).
What is port 9306 used for?
Port 9306 is assigned to sphinxql and uses TCP. The IANA registry describes the service as “Sphinx search server (MySQL listener)”. 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 sphinxql connects to port 9306. If nothing is listening, the connection is refused. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 9306 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.
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Andrew_Aksyonoff].
Check and block port 9306
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 = :9306'Check on Windows
Get-NetTCPConnection -LocalPort 9306 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 9306/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 9306 -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 9306 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 9306 is usually used
Most traffic on port 9306 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Application servers opening pooled connections to the database on port 9306.
- Migrations, backups and reporting jobs run from a trusted bastion host.
- Local Docker or test environments that publish the database on the host.
Open a test connection
Probe the TCP listener before you debug credentials or driver settings.
nc -vz 127.0.0.1 9306Common problems with port 9306
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 9306. 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 = :9306' or sudo lsof -i :9306. 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 9306 at a glance
| Port number | 9306 |
|---|---|
| Service name | sphinxql |
| Transport protocol | TCP |
| Category | Databases |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Registered assignee | [Andrew_Aksyonoff] |
| Registry description | Sphinx search server (MySQL listener) |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 9306 used for?
Port 9306 (SPHINXQL) uses TCP. Sphinx search server (MySQL listener).
How do I check if port 9306 is open?
On Linux run `sudo ss -tlpn 'sport = :9306'`. On Windows run `Get-NetTCPConnection -LocalPort 9306 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 9306; empty output usually means nothing is bound to it.
How do I block port 9306?
With UFW run `sudo ufw deny 9306/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 9306 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 9306 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