How to debug communication error with Shelly Pro 3EM?

sjjh · June 21, 2025, 8:20am

I’m trying to setup OpenEMS Edge & UI (both docker) and added a first component: Energy Meter Shelly Pro 3EM. In the UI I now receive an error “Communication with slave device failed” as system status (cf. below screenshot). The live system log in the UI does not show any error message.
I can successfully ping the device from command line using the IP address supplied to the component instance. docker logs openems_ui does not show any error message.

Any idea how to debug the issue further?

Screenshot of UI system status dialog, showing the error message:

Sn0w3y · June 21, 2025, 8:22am

Seems like a Basic Docker Issue, where your Docker Container is not allowed to Connect “Outside” of itself maybe?!

Also check if your Shelly has a Password on the UI - not supported.

sjjh · June 21, 2025, 11:24am

Thx! That was the cause. Do you know if this is a limitation of the API or if the feature is “just” not implemented?

I’d like to add a note somewhere, that a password on the UI is not supported. Would a comment above line 9 in openems/io.openems.edge.io.shelly/src/io/openems/edge/io/shelly/shellypro3em/IoShellyPro3Em.java at develop · OpenEMS/openems · GitHub be a suitable location, or is there a better place? (I didn’t find a documentation of the supported components with their capabilities and limitation in the documentation yet, otherwise I’d think it would be good to document it there.)

I’d like to improve the error message, giving a hint on how to solve the error^[1], e.g., “Please check the network connection and ensure that the device has no password set in the UI”. I created a pr, happy to get it improved: Update IoShellyPro3Em.java: included remedy for communication error msg by sjjh · Pull Request #3203 · OpenEMS/openems · GitHub

Good error messages should contain a remedy, cf. https://www.nngroup.com/articles/error-message-guidelines/ and Error Messages: 4 Guidelines for Effective Communication (Video) - NN/g ↩︎

Sn0w3y · June 21, 2025, 12:21pm

I would prefer it to add the “Hint” into the

github.com/OpenEMS/openems

io.openems.edge.io.shelly%2Freadme.adoc

develop

= Shelly WiFi Relay Switch

This bundle implements Shelly WiFi Relay Switches and Meters.

Compatible with
- https://www.shelly.com/de/products/shop/1xs25[Shelly 2.5]
- https://www.shelly.com/en/products/shop/shelly-3-em[Shelly 3EM]
- Shelly Plug S
- https://www.shelly.com/de/products/shop/shelly-plus-plug-s-1[Shelly Plus Plug S]
- https://www.shelly.com/de/products/shop/shelly-pro-3-em-120-a-1[Shelly Pro 3EM 3-Phase Meter]
- https://www.shelly.com/de/products/shop/shelly-plus-1-pm[Shelly Plus 1PM]
- https://www.shelly.com/de/products/shop/shelly-pro-3-1[Shelly Pro 3]

https://github.com/OpenEMS/openems/tree/develop/io.openems.edge.io.shelly[Source Code icon:github[]]

as it is related to all shellys..

Also maybe do not create a PR automatically and wait for Feedback - otherwise just create one without a Forum Post as it is not needed then to Inform the Community if the Feedback is given after the PR is already there..

We could also consider to add a Feature to Authenticate with Password aswell.

sjjh · June 21, 2025, 12:40pm

I’ll add it and create a pr.

Will add as feature request.