In the earlier post MKR1000 Azure IoT Hub Interface using HTTP, I wrote about how to get the MKR1000 ready for Azure IoT Hub and start receiving data from Azure IoT. You might have noticed the following when running the sketch in the earlier post: After using the Device Explorer to send a single message, the MKR1000 would have blinked its LED after the first receive. If you continue to let the sketch run with out sending any new message, after about 60 seconds you will notice that MKR1000 receiving the same message and blinking again. This is due to the way a message’s life cycle works on the Azure IoT Hub. In this post I will address how the devices should send any one of Complete/Reject/Abandon message back to the Azure IoT Hub so that the message is not replayed again. This is essential if you are to interface with Azure IoT Hub correctly with HTTP.