Port 9411 ZIPKIN
Port 9411 is the community default for Zipkin, using TCP.
What is port 9411 used for?
Port 9411 is widely used by Zipkin (TCP), a community convention rather than an IANA assignment. Zipkin trace collector, API and web UI port (community convention; not IANA-assigned). 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 Zipkin connects to port 9411. 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 9411 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.
Because this number is not IANA-assigned, a different application may legitimately use it on a machine you do not control. Always identify the actual listening process before deciding that the port belongs to this technology.
Browse all Monitoring and metrics ports
This port number is not assigned by IANA. The entry documents a widely adopted community convention.
Check and block port 9411
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 = :9411'Check on Windows
Get-NetTCPConnection -LocalPort 9411 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 9411/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 9411 -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 9411 safe to expose?
Zipkin's UI and API can expose service topology and trace data. Restrict it to your observability network. Expose this port only when the service is actually needed. Keep it patched, prefer an encrypted alternative, and limit source addresses with a firewall allowlist.
Where port 9411 is usually used
Most traffic on port 9411 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Scrapers such as Prometheus pulling metrics from port 9411 on a schedule.
- Dashboards and alerting rules querying the same endpoint.
- Incident reviews comparing metrics before and after a deployment.
Check the Zipkin health endpoint
Zipkin's health endpoint returns JSON when the collector is ready.
curl -s http://127.0.0.1:9411/healthCommon problems with port 9411
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 9411. 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 = :9411' or sudo lsof -i :9411. 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 9411 at a glance
| Port number | 9411 |
|---|---|
| Service name | Zipkin |
| Transport protocol | TCP |
| Category | Monitoring and metrics |
| Range | Registered port (1024–10000) |
| Risk level | Medium |
| Reference | Community convention (not IANA-assigned) |
| Registry description | Zipkin trace collector, API and web UI port (community convention; not IANA-assigned) |
| Source | Community convention |
Frequently asked questions
What is port 9411 used for?
Port 9411 (ZIPKIN) uses TCP. Zipkin trace collector, API and web UI port (community convention; not IANA-assigned) (community convention, not an IANA assignment).
How do I check if port 9411 is open?
On Linux run `sudo ss -tlpn 'sport = :9411'`. On Windows run `Get-NetTCPConnection -LocalPort 9411 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 9411; empty output usually means nothing is bound to it.
How do I block port 9411?
With UFW run `sudo ufw deny 9411/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 9411 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 9411 safe to expose?
Zipkin's UI and API can expose service topology and trace data. Restrict it to your observability network. Nevertheless, expose this port only when the service is actually needed. Keep it patched, prefer an encrypted alternative, and limit source addresses with a firewall allowlist.
Related ports
- Port 9402 · sec-pc2fax-srvSamsung PC2FAX for Network Server
- Port 9418 · gitgit pack transfer service
- Port 9100 · hp-pdl-datastrPDL Data Streaming Port
- Port 11161 · suncacao-snmpsun cacao snmp access point
- Port 9093 · copycatCopycat database replication service
- Port 12321 · warehouse-sssWarehouse Monitoring Syst SSS
Primary data: IANA Service Name and Transport Protocol Port Number Registry. This number is a community convention, not an IANA assignment.
Last reviewed 2026-10-30 · Methodology · About · Privacy