add subscription example

Author: brentru

examples/aio_basics/adafruitio_01_subscribe.py

@@ -0,0 +1,58 @@
+"""
+'adafruitio_01_subscribe.py'
+==========================
+Subscribes to an Adafruit IO Feed
+
+Author(s): Brent Rubell, Todd Treece for Adafruit Industries
+"""
+# Import standard python modules.
+import sys
+
+# This example uses the MQTTClient, instead of the REST client
+from Adafruit_IO import MQTTClient
+
+# Set to your Adafruit IO key & username below.
+ADAFRUIT_IO_USERNAME = 'YOUR_AIO_USERNAME'
+ADAFRUIT_IO_KEY = 'YOUR_AIO_KEY'
+
+# Set to the ID of the feed to subscribe to for updates.
+FEED_ID = 'counter'
+
+# Define callback functions which will be called when certain events happen.
+def connected(client):
+    """Connected function will be called when the client is connected to Adafruit IO.
+    This is a good place to subscribe to feed changes.  The client parameter
+    passed to this function is the Adafruit IO MQTT client so you can make
+    calls against it easily.
+    """
+    # Subscribe to changes on a feed named Counter.
+    print('Subscribing to Feed {0}'.format(FEED_ID))
+    client.subscribe(FEED_ID)
+    print('Waiting for feed data...')
+
+def disconnected(client):
+    """Disconnected function will be called when the client disconnects."""
+    sys.exit(1)
+
+def message(client, feed_id, payload):
+    """Message function will be called when a subscribed feed has a new value.
+    The feed_id parameter identifies the feed, and the payload parameter has
+    the new value.
+    """
+    print('Feed {0} received new value: {1}'.format(feed_id, payload))
+
+
+# Create an MQTT client instance.
+client = MQTTClient(ADAFRUIT_IO_USERNAME, ADAFRUIT_IO_KEY)
+
+# Setup the callback functions defined above.
+client.on_connect = connected
+client.on_disconnect = disconnected
+client.on_message = message
+
+# Connect to the Adafruit IO server.
+client.connect()
+
+# The first option is to run a thread in the background so you can continue
+# doing things in your program.
+client.loop_blocking()