How to send messages from service worker to the chrome extension without having the webapp open

In the background script we have:

chrome.webRequest.onBeforeRequest.addListener(function (details) {
  if (details.method === 'HEAD') {
    if (details.url.endsWith('?start')) {
      ringSound.play();
    } else if (details.url.endsWith('?stop')) {
      ringSound.pause();
      ringSound.currentTime = 0;
    }
  }
}, { urls: [ 'https://*.gruveo.com/api/ring?*' ] } );

In the webapp we do:

fetch('https://www.gruveo.com/api/ring?' + (start ? 'start' : 'stop'), { method: 'HEAD' }).catch(function () {});

You can get our extension from https://chrome.google.com/webstore/detail/gruveo-instant-connect/jlongfhigcebblbebgmpobcgjhlhegcc and analyze it.

zdila/chrome-bg-with-sw-communication.md