Web Bluetooth / Discover Services & Characteristics (Async Await) Sample

Available in Chrome 55+ | View on GitHub | Browse Samples

The Web Bluetooth API lets websites discover and communicate with devices over the Bluetooth 4 wireless standard using the Generic Attribute Profile (GATT). It is currently partially implemented in Android M, Chrome OS, Linux, and Mac.

This sample illustrates the use of the Web Bluetooth API to discover all accessible primary services with server.getPrimaryServices and their characteristics from a nearby Bluetooth Low Energy Device. You may want to try this demo with the BLE Peripheral Simulator App from the Google Play Store and check out the Discover Services & Characteristics Sample (Promises) sample.

Live Output


JavaScript Snippet

async function onButtonClick() {
  // Validate services UUID entered by user first.
  let optionalServices = document.querySelector('#optionalServices').value
    .split(/, ?/).map(s => s.startsWith('0x') ? parseInt(s) : s)
    .filter(s => s && BluetoothUUID.getService);

  try {
    log('Requesting any Bluetooth Device...');
    const device = await navigator.bluetooth.requestDevice({
     // filters: [...] <- Prefer filters to save energy & show relevant devices.
        acceptAllDevices: true,
        optionalServices: optionalServices});

    log('Connecting to GATT Server...');
    const server = await device.gatt.connect();

    // Note that we could also get all services that match a specific UUID by
    // passing it to getPrimaryServices().
    log('Getting Services...');
    const services = await server.getPrimaryServices();

    log('Getting Characteristics...');
    for (const service of services) {
      log('> Service: ' + service.uuid);
      const characteristics = await service.getCharacteristics();

      characteristics.forEach(characteristic => {
        log('>> Characteristic: ' + characteristic.uuid + ' ' +
            getSupportedProperties(characteristic));
      });
    }
  } catch(error) {
    log('Argh! ' + error);
  }
}

/* Utils */

function getSupportedProperties(characteristic) {
  let supportedProperties = [];
  for (const p in characteristic.properties) {
    if (characteristic.properties[p] === true) {
      supportedProperties.push(p.toUpperCase());
    }
  }
  return '[' + supportedProperties.join(', ') + ']';
}