node URI Beacon Scanner

uri-beacon-test.js

var UriBeacon = require('./uri-beacon');

UriBeacon.on('discover', function(uriBeacon) {
  console.log('discovered: ' + JSON.stringify(uriBeacon, null, 2));
});

UriBeacon.startScanning();

uri-beacon.js

var events = require('events');
var util = require('util');

var debug = require('debug')('uri-beacon');

var noble = require('noble');

var SERVICE_UUID = 'fed8';

var PREFIXES = [
  'http://www.',
  'https://www.',
  'http://',
  'https://',
  'urn:uuid:'
];

var SUFFIXES = [
  '.com/',
  '.org/',
  '.edu/',
  '.net/',
  '.info/',
  '.biz/',
  '.gov/',
  '.com',
  '.org',
  '.edu',
  '.net',
  '.info',
  '.biz',
  '.gov'
];

var UriBeacon = function() {
  noble.on('discover', this.onDiscover.bind(this));
};

util.inherits(UriBeacon, events.EventEmitter);

UriBeacon.prototype.startScanning = function() {
  debug('startScanning');

  var startScanningOnPowerOn = function() {
    if (noble.state === 'poweredOn') {
      noble.startScanning([SERVICE_UUID], true);
    } else {
      noble.once('stateChange', startScanningOnPowerOn);
    }
  };

  startScanningOnPowerOn();
};

UriBeacon.prototype.stopScanning = function() {
  debug('stopScanning');
  noble.stopScanning();
};

UriBeacon.prototype.onDiscover = function(peripheral) {
  debug('onDiscover: %s', peripheral);

  var serviceData = peripheral.advertisement.serviceData;
  var rssi = peripheral.rssi;

  debug('onDiscover: serviceData = %s, rssi = %d', serviceData ?  serviceData.toString('hex') : null, rssi);

  if (serviceData &&
        serviceData.length === 1 &&
        serviceData[0].uuid === SERVICE_UUID) {

    var uriBeaconData = serviceData[0].data;
    var flags = uriBeaconData.readUInt8(0);
    var txPower = uriBeaconData.readInt8(1);
    var uriData = uriBeaconData.slice(2);

    var uriPrefix = '';
    var uriSuffix = '';

    var firstByte = uriData[0];
    var lastByte = uriData[uriData.length - 1];

    if (firstByte < PREFIXES.length) {
      uriPrefix = PREFIXES[firstByte];
      uriData = uriData.slice(1);
    }

    if (lastByte < SUFFIXES.length) {
      uriSuffix = SUFFIXES[lastByte];
      uriData = uriData.slice(0, uriData.length - 1);
    }

    var uri = uriPrefix + uriData.toString() + uriSuffix;

    var uriBeacon = {
      flags: flags,
      txPower: txPower,
      uri: uri,
      rssi: rssi
    };

    debug('onDiscover: uriBeacon = %s', JSON.stringify(uriBeacon));
    this.emit('discover', uriBeacon);
  }
};

module.exports = new UriBeacon();