What you need to know about accessing AI agent interfaces and monitoring tools on ports 9090 and 9091
If you’ve been working with local AI agents or DevOps monitoring stacks, you’ve likely encountered the address localhost:9090. It’s a port number that pops up frequently, especially when you’re running tools like the OpenClaw autonomous AI agent or the Prometheus metrics system. But what exactly lives there, and why do we sometimes see port 9091 instead? Let’s walk through the common uses, troubleshooting steps, and a few tips for sharing your dashboard with others.
Which Services Typically Use Port 9090?
Port 9090 is a popular choice for web interfaces that need a dedicated spot away from the more crowded lower ports like 8080 or 3000. Here are a few tools that often claim it:
-
OpenClaw AI – This local agent uses port
9090for its Web UI and WebSocket Gateway, letting you monitor logs, adjust settings, and see how the agent interacts with messaging platforms like Telegram or Discord. - Cockpit – A server management tool that also defaults to port 9090 for its web console.
- Prometheus – The well‑known monitoring and time‑series database uses port 9090 as its default for the web interface.
-
Various Exporters – Some Prometheus exporters may fall back to port
9091if9090is already taken.
Because OpenClaw and Prometheus both gravitate toward 9090, conflicts can happen. When that occurs, the second service might automatically shift to 9091 – which explains why you’ll sometimes see both ports in use.
How to Troubleshoot Localhost:9090
If you type http://localhost:9090 into your browser and nothing loads, don’t panic. A few simple checks can usually get you back on track.
Step 1: Verify the Service Is Running
First, make sure the application you’re expecting (OpenClaw, Prometheus, etc.) has actually started. Look at the terminal where you launched it – are there any error messages? Did it finish its boot sequence?
Step 2: Try Port 9091
Because of the overlap between Prometheus and OpenClaw, the software might have automatically switched to the next available port. Open http://localhost:9091 and see if your dashboard appears there.
Step 3: Test with a Command Line Tool
You can also use curl to get a quick response. Run:
curl http://localhost:9090
If the service is alive, you’ll likely see some HTML or a JSON response. A connection refused message means nothing is listening on that port.
Sharing Your Dashboard with Other Devices
Sometimes you need to access your local dashboard from a different machine or show it to a colleague. A handy method is to use a tunnel service like Pinggy. It creates a temporary public URL that forwards traffic to your local port.
Run this command (replace free.pinggy.io with your service if needed):
ssh -p 443 -R0:localhost:9090 free.pinggy.io
After running it, you’ll get a URL you can share. Just keep in mind: if your dashboard controls an AI agent or exposes sensitive data, make sure authentication is turned on before opening it to the wider internet.
Common Problems and How to Fix Them
Here are two frequent headaches with port 9090 and the usual remedies.
“Connection Refused” Error
Problem: The browser says it can’t connect.
Solution: Double‑check that the server process actually started without errors. Sometimes a configuration typo or missing dependency prevents the service from binding to the port. Restart the service and watch the logs.
“Port Already in Use” Error
Problem: You try to start OpenClaw (or Prometheus) and get a message that port 9090 is already taken.
Solution: Find out which process is using it with:
lsof -i :9090
The output will show the PID and name of the program. You can either stop that process or reconfigure one of the applications to use a different port (like 9091) by editing its configuration file.
Quick Commands to Diagnose Port 9090
For a fast check on what’s occupying port 9090, keep these commands handy:
- List the process using port
9090:
lsof -i :9090
- Test connectivity and see response headers:
curl -I http://localhost:9090
- Check if the port is listening from another machine (if networking allows):
nc -zv localhost 9090
Conclusion
Ports 9090 and 9091 have become the de facto home for several important local web UIs, from AI agent dashboards to monitoring consoles. Understanding how they’re used, how to troubleshoot them, and how to share them safely can save you time and frustration. Whether you’re tweaking an OpenClaw agent or checking Prometheus metrics, knowing your way around these ports makes the whole experience smoother.
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