Skip to content


Getting Started


SocketProtocolError in Debug Console

You may see the following SocketProtocolError message in the Debug Console once you have started your SAFE application.

WebSocket connection to 'ws://localhost:8000/socketcluster/' failed: Error during WebSocket handshake: Unexpected response code: 404

Whilst these messages can be safely ignored, you can eliminate them by installing Redux Dev Tools in the launched Chrome instance as described in the debugging prerequisites section.

Debugging in VS Code

Node Process does not stop after stopping the debugger

VS Code does not kill the Fable process when you stop the debugger, leaving it running as a "zombie". In such a case, you will have to explicitly kill the process otherwise it will hold onto port 8080 and prevent you starting new instances. This should be easily doable by sending Ctrl+C in the Terminal window in VS Code for Watch Client task. Tracked here.

Chrome opens to a blank window

  • Occasionally, VS Code will open Chrome before the Client has started. In this case, you will be presented with a blank screen until the client starts.
  • Depending on the order in which compilation occurs, VS Code may launch the web browser before the server has started. If this occurs, you may need to refresh the browser once the server is fully initialised.


JavaScript bundle size

A project created from SAFE template might issue the following warning from Webpack upon building the JavaScript bundle:

WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.

We're striving to optimise the bundle size, however with a number of different options and dependencies it's not that easy to stay below the Webpack recommended limit.

To minimize the bundle size in your project you can try restricting browser compatibility by modifying the Babel Preset targets for Browserslist and thus using less polyfills.

For more info, see this issue.