how to receive data from bluetooth device using node.js

Question

I am new to javascript and node.js. Currently am working in medical project. First i will explain my work. I have to receive data from Bluetooth device (normal BP rate ,pulse rate ) and display the readings in the web app using node.js. I don't know how to receive data from Bluetooth device (patient monitor machine) can you guys suggest me some blogs or books to read. Thanks in advance.

Answer 1

You can use "node-bluetooth" to send and receive data from and to a device respectively. This is a sample code:-

const bluetooth = require('node-bluetooth');

// create bluetooth device instance

const device = new bluetooth.DeviceINQ();

device
    .on('finished', console.log.bind(console, 'finished'))
    .on('found', function found(address, name) {
        console.log('Found: ' + address + ' with name ' + name);

        device.findSerialPortChannel(address, function(channel) {
            console.log('Found RFCOMM channel for serial port on %s: ', name, channel);

            // make bluetooth connect to remote device
            bluetooth.connect(address, channel, function(err, connection) {
                if (err) return console.error(err);
                connection.write(new Buffer('Hello!', 'utf-8'));
            });

        });

        // make bluetooth connect to remote device
        bluetooth.connect(address, channel, function(err, connection) {
            if (err) return console.error(err);

            connection.on('data', (buffer) => {
                console.log('received message:', buffer.toString());
            });

            connection.write(new Buffer('Hello!', 'utf-8'));
        });
    }).inquire();

It scans for the device name given in "device" variable.

Answer 2

You can use node-ble a Node.JS library that leverages on D-Bus and avoids C++ bindings. https://github.com/chrvadala/node-ble

Here a basic example

async function main () {
  const { bluetooth, destroy } = createBluetooth()

  // get bluetooth adapter
  const adapter = await bluetooth.defaultAdapter()
  await adapter.startDiscovery()
  console.log('discovering')

  // get device and connect
  const device = await adapter.waitDevice(TEST_DEVICE)
  console.log('got device', await device.getAddress(), await device.getName())
  await device.connect()
  console.log('connected')

  const gattServer = await device.gatt()

  // read write characteristic
  const service1 = await gattServer.getPrimaryService(TEST_SERVICE)
  const characteristic1 = await service1.getCharacteristic(TEST_CHARACTERISTIC)
  await characteristic1.writeValue(Buffer.from('Hello world'))
  const buffer = await characteristic1.readValue()
  console.log('read', buffer, buffer.toString())

  // subscribe characteristic
  const service2 = await gattServer.getPrimaryService(TEST_NOTIFY_SERVICE)
  const characteristic2 = await service2.getCharacteristic(TEST_NOTIFY_CHARACTERISTIC)
  await characteristic2.startNotifications()
  await new Promise(done => {
    characteristic2.once('valuechanged', buffer => {
      console.log('subscription', buffer)
      done()
    })
  })

  await characteristic2.stopNotifications()
  destroy()
}