Update readme to use the latest Event Hubs SDK (#23)

Author: ramya-rao-a

iot-hub/Quickstarts/read-d2c-messages/Readme.md

@@ -1,15 +1,45 @@
 # Read device to cloud messages (Python)
 
-Currently there is no pip available for the Azure Event Hubs client.
+Use the Microsoft Azure Event Hubs Client for Python to read messages sent from a device by using the
+built-in event hubs that exists by default for every Iot Hub instance. For more details, see the 
+documentation for the [azure-eventhub](https://pypi.org/project/azure-eventhub/) package.
 
-The options are:
+## Get Event Hubs-compatible connection string
+
+You can get the Event Hubs-compatible connection string to your IotHub instance via the Azure portal or
+by using the Azure CLI.
+
+If using the Azure portal, see [Built in endpoints for IotHub](https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-read-builtin#read-from-the-built-in-endpoint) to get the Event Hubs-compatible
+connection string.
+
+If using the Azure CLI, you will need to run the below to get the Event Hubs-compatible endpoint, path
+and the SAS key for the "service" policy.
+
+- `az iot hub show --query properties.eventHubEndpoints.events.endpoint --name {your IoT Hub name}`
+- `az iot hub show --query properties.eventHubEndpoints.events.path --name {your IoT Hub name}`
+- `az iot hub policy show --name service --query primaryKey --hub-name {your IoT Hub name}`
+
+Then, form the Event Hubs-compatible connection string as below
+`Endpoint=eventHubsCompatibleEndpoint/;EntityPath=eventHubsCompatiblePath;SharedAccessKeyName=service;SharedAccessKey=iotHubSasKey`.
+
+With the Event Hubs-compatible connection string now in hand, you can now use the EventHubConsumerClient from the
+[azure-eventhub](https://pypi.org/project/azure-eventhub/) package as shown in any of the receive related samples below
+- [sync samples](https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/eventhub/azure-eventhub/samples/sync_samples)
+- [async samples](https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/eventhub/azure-eventhub/samples/async_samples)
+
+If you cannot get the Event Hubs-compatible connection string in the above manner, and need to programatically get this information,
+then use the [sample to convert IotHub connection string to an Event Hubs-compatible one](https://github.com/Azure/azure-sdk-for-python/blob/master/sdk/eventhub/azure-eventhub/samples/async_samples/iot_hub_connection_string_receive_async.py). This conversion is done by connecting to 
+the IoT hub endpoint and receiving a redirection address to the built-in event hubs. This address is then used 
+in the Event Hubs Client to read messages.
+
+## Checkpointing
+
+For an example that uses checkpointing, use the checkpoint store from
+- [azure-eventhub-checkpointstoreblob](https://pypi.org/project/azure-eventhub-checkpointstoreblob/) package for sync
+- [azure-eventhub-checkpointstoreblob-aio](https://pypi.org/project/azure-eventhub-checkpointstoreblob-aio/) package for async
+
+The above links have documentation on samples on how to use the checkpoint store.
 
-* Build a docker image.
-* Build the libraries manually.
 
-For more information, see https://github.com/Azure/azure-event-hubs-python
 
-To keep this quickstart simple, you are using the iothub-explorer CLI tool to monitor telemetry sent to the hub:
 
-npm install -g iothub-explorer
-iothub-explorer monitor-events MyPythonDevice --login {your hub service connection string}