let options = {
                    filters: [
                      { namePrefix: discoveryNamePrefix }
                    ],
                    acceptAllDevices: false,
                    optionalServices: discoveryOptionalServices
                  }

                  navigator.bluetooth.requestDevice(options)
                    .then(device => {
                      bluetoothDevice = device;
                      bluetoothDevice.addEventListener('gattserverdisconnected', onDeviceDisconnected);
                      return bluetoothDevice.gatt.connect()
                    })
                    .then(server => {
                      return server.getPrimaryServices();
                    })
                    .then(services => {
                      let promises = services.map(function(service) {
                        return service.getCharacteristics()
                        .then(characteristics => {
                          characteristics.forEach(characteristic => {
                            if(service.uuid==getCanonicalUUID(serviceDeviceInfoId))
                              serviceDeviceInfoChars.push({ key: characteristic.uuid, value: characteristic });
                            else if(service.uuid==getCanonicalUUID(serviceMonitorId))
                              serviceMonitorChars.push({ key: characteristic.uuid, value: characteristic });
                          });
                        })
                        .then(_ => { return service });
                      });

                      return Promise.all(promises);
                    })
                    .then(services => {
                      let charRelease = serviceDeviceInfoChars.find(o => o.key === getCanonicalUUID(0x4));
                      charRelease.value.readValue()
                        .then(value => {
                          console.log(decodeDataViewToString(value))
                        });

                      onDeviceConnected(bluetoothDevice);
                    })
                    .catch(error => {
                      onDeviceFailedToConnect(error);
                    });
                }
              });