I've been going crazy for a few days with my IoT Hub and I can't figure out why.
On my devices, I have connected about 60-70 of them, the C2D messaging system doesn't work anymore.
My "system" is very simple, it is based on an embedded Linux distribution and I have a script written in C that is invoked every 10'' to send a teletrics message to IoT Hub, so far so good, everything works correctly and never had any problems.
I use mosquitto and MQTT protocol.
Every x seconds, depending on the device, a Subscribe request is also made via another script written in C.
The connection is successfully made to IoT Hub, but the device no downloads the message, it is as if it did not receive it.
My scripts, both the one for sending telemetry and the one for receiving messages are based on the C codes downloaded from here:
My devices authenticate with X.509 certificates and everything has always worked properly, I have been using this system for almost a year.
In the past few days I started having problems on sending messages from cloud to device: from Azure interface the message shows correctly sent and queued, but to the device it is as if it never arrives.
I thought that for some reason the post script might conflict with the subscribe script but I noticed that the problem persists even when running only the subscribe script.
To rule out the possibility that the problem could be associated with the platform, I also used the C program in the Linux Ubuntu environment. The problem persists.
Has something changed in Azure IoT Hub that I missed?
Has anyone experienced similar problems?
I am very concerned because I need to restore this "communication" as soon as possible but I don't know how to do it.
Thanks to everybody.