Web Bluetooth / Discover Services & Characteristics Sample

Available in Chrome 53+ | 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 (Async Await) sample.

Live Output


JavaScript Snippet

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);

  log('Requesting any Bluetooth Device...');
  navigator.bluetooth.requestDevice({
   // filters: [...] <- Prefer filters to save energy & show relevant devices.
      acceptAllDevices: true,
      optionalServices: optionalServices})
  .then(device => {
    log('Connecting to GATT Server...');
    return device.gatt.connect();
  })
  .then(server => {
    // Note that we could also get all services that match a specific UUID by
    // passing it to getPrimaryServices().
    log('Getting Services...');
    return server.getPrimaryServices();
  })
  .then(services => {
    log('Getting Characteristics...');
    let queue = Promise.resolve();
    services.forEach(service => {
      queue = queue.then(_ => service.getCharacteristics().then(characteristics => {
        log('> Service: ' + service.uuid);
        characteristics.forEach(characteristic => {
          log('>> Characteristic: ' + characteristic.uuid + ' ' +
              getSupportedProperties(characteristic));
        });
      }));
    });
    return queue;
  })
  .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(', ') + ']';
}