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ERR_NGROK_8012

Message​

Traffic was successfully tunneled to the ngrok agent, but the agent failed to establish a connection to the upstream web service at ADDR.

Overview​

This error occurs when the ngrok agent successfully receives traffic but fails to establish a connection with your local service (the "upstream" service). While the tunnel is created successfully, ngrok cannot forward the traffic to your application.

Common Issues and Solutions​

  1. Local Service Not Running or Inaccessible

    Cause: The web service or application on your local machine is not active or cannot be reached.

    Resolution:

    • Start your local service.
    • Confirm you can access it directly (e.g., http://localhost:8080).
    • Restart ngrok with the correct port number.

  2. Incorrect Port Specified

    Cause: The port in your ngrok command doesn't match your local service's port.

    Resolution:

    • Verify the port your local service is using.
    • Update your ngrok command to use the correct port.
    • Example: Use ngrok http 3000 if your service runs on port 3000.

General Troubleshooting Steps​

  1. Verify local service accessibility without ngrok.
  2. Ensure the latest ngrok version is installed.
  3. Restart the ngrok agent.

Further help​

If you're having trouble resolving this error, please reach out to support@ngrok.com