Add support for MQTT pver SSL and update to attemp disconnects and extra loggin on mqtt failures

.gitignore

@@ -135,3 +135,6 @@ log.txt
 uploads/
 readings/
 rain.txt
+
+# Pycharm idea
+.idea/

documentation/destinations/mqtt.md

@@ -14,6 +14,14 @@ We recommend [Mosquitto](https://mosquitto.org/) which is an open source and lig
 
 Steve's Internet Guide has instructions for installing Mosquitto on both [Windows](http://www.steves-internet-guide.com/install-mosquitto-broker/) and [Linux](http://www.steves-internet-guide.com/install-mosquitto-linux/) which are worth checking out.
 
+## Support for local SSL with MQTT Broker
+
+1 > Upload the certificate file to your pico for example a file called ca.crt 
+
+2 > Update the config.py file and add the line `mqtt_broker_ca_file = 'ca.crt'` replacing ca.crt with the path to the file
+
+The mqtt.py destination file will attempt top use SSL if the `mqtt_broker_ca_file` is not none. 
+
 ## Using a cloud hosted MQTT broker
 
 Alternatively you can avoid any software setup and having to manage your own server by using one of the many hosted MQTT broker services. These generally come with a small monthly fee (£3-5) or have very limited capabilities.

enviro/config_template.py

@@ -30,6 +30,8 @@
 mqtt_broker_address = None
 mqtt_broker_username = None
 mqtt_broker_password = None
+# mqtt broker if using local SSL
+mqtt_broker_ca_file = None
 
 # adafruit ui settings
 adafruit_io_username = None

enviro/destinations/mqtt.py

@@ -12,15 +12,48 @@ def upload_reading(reading):
   username = config.mqtt_broker_username
   password = config.mqtt_broker_password
   nickname = reading["nickname"]
-
+
+  # check if ca file paramter is set, if not set it to not use SSL by setting to None
+  try:
+    config.mqtt_broker_ca_file
+  except AttributeError: 
+    config.mqtt_broker_ca_file = None
+
   try:
-    # attempt to publish reading
-    mqtt_client = MQTTClient(reading["uid"], server, user=username, password=password, keepalive=60)
+    if config.mqtt_broker_ca_file:
+    # Using SSL
+      f = open("ca.crt")
+      ssl_data = f.read()
+      f.close()
+      mqtt_client = MQTTClient(reading["uid"], server, user=username, password=password, keepalive=60,
+                               ssl=True, ssl_params={'cert': ssl_data})
+    else:
+    # Not using SSL
+      mqtt_client = MQTTClient(reading["uid"], server, user=username, password=password, keepalive=60)
+    # Now continue with connection and upload
     mqtt_client.connect()
     mqtt_client.publish(f"enviro/{nickname}", ujson.dumps(reading), retain=True)
     mqtt_client.disconnect()
     return UPLOAD_SUCCESS
-  except:
-    logging.debug(f"  - an exception occurred when uploading")
+
+  # Try disconneting to see if it prevents hangs on this typew of errors recevied so far
+  except (OSError, IndexError) as exc:
+    try:
+      import sys, io
+      buf = io.StringIO()
+      sys.print_exception(exc, buf)
+      logging.debug(f"  - an exception occurred when uploading.", buf.getvalue())
+      mqtt_client.disconnect()
+    except Exception as exc:
+      import sys, io
+      buf = io.StringIO()
+      sys.print_exception(exc, buf)
+      logging.debug(f"  - an exception occurred when disconnecting mqtt client.", buf.getvalue())
+
+  except Exception as exc:
+    import sys, io
+    buf = io.StringIO()
+    sys.print_exception(exc, buf)
+    logging.debug(f"  - an exception occurred when uploading.", buf.getvalue())
 
   return UPLOAD_FAILED