Arduino cloud devices have stopped working

Development Tools Cloud IoT
1

I have several devices that connect to the Arduino Cloud. Recently all of my devices have stopped connecting which I understand is because the CA was rolled over due to a security issue.

I've tried to reflash a few of the devices but nothing will connect again.

I regenrated the certificates and tried to delete the thing, device, created a new sketch with no luck.

I still get this error after the device connects to WiFi.

ArduinoIoTCloudTCP::handle_ConnectMqttBroker could not connect to mqtts-up.iot.arduino.cc:8884
ArduinoIoTCloudTCP::handle_ConnectMqttBroker 8 connection attempt at tick time 209155
T 79.6 F | H 41.2 % | V 2.20 V

The Arduino client is giving me this error.

2025/06/14 15:26:40 http: TLS handshake error from 127.0.0.1:34932: client sent an HTTP request to an HTTPS server

I'm not sure how to troubleshoot this since there are no logs or any more data available to me.

What can I do to get these devices connected again?

2

Maybe try the Agent

Screenshot 2025-06-14 at 18.51.59
Screenshot 2025-06-14 at 18.51.59442×424 50.9 KB

3

image
image250×214 7.96 KB

It's greyed out on mine.

4

Hi @orsty3001, what kind of device are you connecting? The 8884 port is for devices connecting with device_id + secret, not for the devices using certificates. Something's wrong with the configuration, do you pass any additional parameter to the ArduinoIoTCloud.connect()?

5

I just figured this out. My ISP’s DNS is filtering the the ip address for mqtts-up.iot.arduino.cc for some reason. They redirect it to 0.0.0.0. What was confusing me is my laptop is on a different network that provides a different DNS server address over DHCP. So when I tried to resolve the mqtt url it looked good.

For anyone in the future there is two ways to fix this. Change the DNS server to something else in your DHCP service or hardcode a DNS server into your project.

This can be marked as solved now.

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