Merge pull request noble#802 from don/echo-example

connect to bleno echo service example

examples/echo.js

@@ -0,0 +1,75 @@
+// Connect to a peripheral running the echo service
+// https://github.com/noble/bleno/blob/master/examples/echo
+
+// subscribe to be notified when the value changes
+// start an interval to write data to the characteristic
+
+//const noble = require('noble');
+const noble = require('..');
+
+const ECHO_SERVICE_UUID = 'ec00';
+const ECHO_CHARACTERISTIC_UUID = 'ec0e';
+
+noble.on('stateChange', state => {
+  if (state === 'poweredOn') {
+    console.log('Scanning');
+    noble.startScanning([ECHO_SERVICE_UUID]);
+  } else {
+    noble.stopScanning();
+  }
+});
+
+noble.on('discover', peripheral => {
+    // connect to the first peripheral that is scanned
+    noble.stopScanning();
+    const name = peripheral.advertisement.localName;
+    console.log(`Connecting to '${name}' ${peripheral.id}`);
+    connectAndSetUp(peripheral);
+});
+
+function connectAndSetUp(peripheral) {
+
+  peripheral.connect(error => {
+    console.log('Connected to', peripheral.id);
+
+    // specify the services and characteristics to discover
+    const serviceUUIDs = [ECHO_SERVICE_UUID];
+    const characteristicUUIDs = [ECHO_CHARACTERISTIC_UUID];
+
+    peripheral.discoverSomeServicesAndCharacteristics(
+        serviceUUIDs,
+        characteristicUUIDs,
+        onServicesAndCharacteristicsDiscovered
+    );
+  });
+
+  peripheral.on('disconnect', () => console.log('disconnected'));
+}
+
+function onServicesAndCharacteristicsDiscovered(error, services, characteristics) {
+  console.log('Discovered services and characteristics');
+  const echoCharacteristic = characteristics[0];
+
+  // data callback receives notifications
+  echoCharacteristic.on('data', (data, isNotification) => {
+    console.log('Received: "' + data + '"');
+  });
+
+  // subscribe to be notified whenever the peripheral update the characteristic
+  echoCharacteristic.subscribe(error => {
+    if (error) {
+      console.error('Error subscribing to echoCharacteristic');
+    } else {
+      console.log('Subscribed for echoCharacteristic notifications');
+    }
+  });
+
+  // create an interval to send data to the service
+  let count = 0;
+  setInterval(() => {
+    count++;
+    const message = new Buffer('hello, ble ' + count, 'utf-8');
+    console.log("Sending:  '" + message + "'");
+    echoCharacteristic.write(message);
+  }, 2500);
+}