NativeScript plugin

Use when you want to

scan for Bluetooth LE / Smart peripherals,
connect to those peripherals,
read values of a characteristic,
write new values to them,
get notified when the value of a characteristic changes.

Supported platforms

iOS
Android 4.3 and up

Note that a simulator can't be used to test conneting to Bluetooth peripherals.

Installation

From the command prompt go to your app's root folder and execute:

tns plugin add nativescript-bluetooth

And do yourself a favor by adding TypeScript support to your nativeScript app:

tns install typescript

API

Want to dive in quickly? Check out the demo app! Otherwise, mix and match these functions as you see fit:

isBluetoothEnabled

Reports if bluetooth is enabled.

// require the plugin
var bluetooth = require("nativescript-bluetooth");

bluetooth.isBluetoothEnabled().then(
  function(enabled) {
    console.log("Enabled? " + enabled);
  }
);

hasCoarseLocationPermission

On Android 6 you need to request permission to be able to interact with a Bluetooth peripheral (when the app is in the background) when targeting API level 23+. Even if the uses-permission tag for ACCESS_COARSE_LOCATION is present in AndroidManifest.xml.

Note that for BLUETOOTH and BLUETOOTH_ADMIN you don't require runtime permission; adding those to AndroidManifest.xml suffices (which the plugin does for you).

Note that hasCoarseLocationPermission will return true when:

You're running this on iOS, or
You're targeting an API level lower than 23, or
You're using a device running Android < 6, or
You've already granted permission.

bluetooth.hasCoarseLocationPermission().then(
  function(granted) {
    // if this is 'false' you probably want to call 'requestCoarseLocationPermission' now
    console.log("Has Location Permission? " + granted);
  }
);

requestCoarseLocationPermission

// if no permission was granted previously this will open a user consent screen
bluetooth.requestCoarseLocationPermission().then(
  function() {
    console.log("Location permission requested");
  }
);

startScanning

A few of the optional params require a bit of explanation:

seconds

Scanning for peripherals drains the battery quickly, so you better not scan any longer than necessary. If a peripheral is in range and not engaged in another connection it usually pops up in under a second. If you don't pass in a number of seconds you will need to manually call stopScanning.

serviceUUIDs

It's inefficient to scan for all available Bluetooth peripherals and have them report all services they offer.

If you're only interested in finding a heartrate peripheral for instance, pass in service UUID '180d' like this: serviceUUIDs: ['180d']. If you add 2 or more (comma separated) services then only peripherals supporting ALL those services will match.

Note that UUID's are ALWAYS strings; don't pass integers.

onDiscovered

While scanning the plugin will immediately report back uniquely discovered peripherals. This function will receive an object representing the peripheral which contains the properties UUID, name and RSSI (relative signal strength).

bluetooth.startScanning({
  serviceUUIDs: [],
  seconds: 4,
  onDiscovered: function (peripheral) {
  	console.log("Periperhal found with UUID: " + peripheral.UUID);
  }
}).then(function() {
  console.log("scanning complete");
}, function (err) {
  console.log("error while scanning: " + err);
});

stopScanning

At any time during a scan, being one where you passed in a number or seconds or not, you can stop the scan by calling this function.

You may for instance want to stop scanning when the peripheral you found in startScanning's onDiscovered callback matches your criteria.

bluetooth.stopScanning().then(function() {
  console.log("scanning stopped");
});

connect

Pass in the UUID of the peripheral you want to connect to and once a connection has been established the onConnected callback function will be invoked. This callback will received the peripheral object as before, but it's now enriched with a services property. An example of the returned peripheral object could be:

  peripheral: {
    UUID: '3424-542-4534-53454',
    name: 'Polar P7 Heartrate Monitor',
    RSSI: '-57',
    services: [{    
      UUID: '180d',
      name: 'Heartrate service',
      characteristics: [{
        UUID: '34534-54353-234324-343',
        name: 'Heartrate characteristic',
        properties: {
          read: true,
          write: false,
          writeWithoutResponse: false,
          notify: true
        }
      }]
    }]
  }

Here's the connect function in action with an implementation of onConnected that simply dumps the entire peripheral object to the console:

bluetooth.connect({
  UUID: '04343-23445-45243-423434',
  onConnected: function (peripheral) {
  	console.log("Periperhal connected with UUID: " + peripheral.UUID);

  	// the peripheral object now has a list of available services:
  	peripheral.services.forEach(function(service) {
  	  console.log("service found: " + JSON.stringify(service));
   });
  },
  onDisconnected: function (peripheral) {
  	console.log("Periperhal disconnected with UUID: " + peripheral.UUID);
  }
});

Also note that onDisconnected function: if you try to interact with the peripheral after this event you risk crashing your app.

disconnect

Once done interacting with the peripheral be a good citizen and disconnect. This will allow other applications establishing a connection.

bluetooth.disconnect({
  UUID: '34234-5453-4453-54545'
}).then(function() {
  console.log("disconnected successfully");
}).then(function(err) {
  // in this case you're probably best off treating this as a disconnected peripheral though
  console.log("disconnection error: " + err);
});

read

If a peripheral has a service that has a characteristic where properties.read is true then you can call the read function to retrieve the current state (value) of the characteristic.

The promise will receive an object like this:

{
  value: <ArrayBuffer>, // an ArrayBuffer which you can use to decode (see example below)
  valueRaw: <72>, // the platform-specific binary value of the characteristic: NSData (iOS), byte[] (Android)
  characteristicUUID: '434234-234234-234234-434'
}

Armed with this knowledge, let's invoke the read function:

bluetooth.read({
  peripheralUUID: '34234-5453-4453-54545',
  serviceUUID: '180d',
  characteristicUUID: '3434-45234-34324-2343'
}).then(function(result) {
  // fi. a heartrate monitor value (Uint8) can be retrieved like this:
  var data = new Uint8Array(result.value);
  console.log("Your heartrate is: " + data[1] + " bpm");  
}).then(function(err) {
  console.log("read error: " + err);
});

write

If a peripheral has a service that has a characteristic where properties.write is true then you can call the write function to update the current state (value) of the characteristic.

The value must be hexadecimal, so if you want to send a 1, send 0x01. If you want to send multiple bytes add a comma: "0x007F,0x006E".

bluetooth.write({
  peripheralUUID: '34134-5453-4453-54545',
  serviceUUID: '180e',
  characteristicUUID: '3424-45234-34324-2343',
  value: '0x01' // a hex 1
}).then(function(result) {
  console.log("value written");
}).then(function(err) {
  console.log("write error: " + err);
});

writeWithoutResponse

Same API as write, except that when the promise is invoked the value has not been written yet; it has only been requested to be written an no response will be received when it has.

startNotifying

If a peripheral has a service that has a characteristic where properties.notify is true then you can call the startNotifying function to retrieve the value changes of the characteristic.

Usage is very much like read, but the result won't be sent to the promise, but to the onNotify callback function you pass in. This is because multiple notifications can be received and a promise can only resolve once. The value of the object sent to onNotify is the same as the one you get in the promise of read.

bluetooth.startNotifying({
  peripheralUUID: '34234-5453-4453-54545',
  serviceUUID: '180d',
  characteristicUUID: '3434-45234-34324-2343',
  onNotify: function (result) {
    // see the read example for how to decode ArrayBuffers
	console.log("read: " + JSON.stringify(result));
  }  
}).then(function() {
  console.log("subscribed for notifications");
});

stopNotifying

Enough is enough. When you're no longer interested in the values the peripheral is sending you do this:

bluetooth.stopNotifying({
  peripheralUUID: '34234-5453-4453-54545',
  serviceUUID: '180d',
  characteristicUUID: '3434-45234-34324-2343'
}).then(function() {
  console.log("unsubscribed for notifications");
}, function (err) {
  console.log("unsubscribe error: " + err);
});

Changelog

1.1.4 TypeScript fix and TS definition fix in package.json
1.1.3 TypeScript fix
1.1.2 Better Android M compatibility
1.1.1 Better Android permission handling
1.1.0 To be compatible with any Bluetooth device out there, the value returned from read and notify is now an ArrayBuffer.
1.0.0 Initial release

Future work

Find an even better way to write values.
Support other properties of a characteristic.
Report advertising data peripherals broadcast.
Support interacting with multiple characteristics of the same peripheral at the same time.

License

iesrbt/nativescript-bluetooth

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