ble-server/app.js

const bleno = require('bleno')
const config = require('./config.json')
const adapterName = 'BLE_Printer'
const serverUUID = config.uuid.main

const MainService = require('./main-service')

bleno.on('stateChange', state => {
  console.log(`bt device state ${state}`)
  if (state == 'poweredOn') {

    bleno.startAdvertising(adapterName, [serverUUID], (error) => {

    })
  } else {
    bleno.stopAdvertising()
  }
})

bleno.on('advertisingStart', function (error) {
  console.log('on -> advertisingStart: ' + (error ? 'error ' + error : 'success'));

  if (!error) {
    bleno.setServices([new MainService()], error => {
      console.log('set service', error)
    })
  }
})