Problems connecting to Google IoT core via MQTT in C - c

Question

I've set up the sample program from here: https://github.com/GoogleCloudPlatform/cpp-docs-samples/tree/master/iot/mqtt-ciotc
When I try to run the example, the only error message that I get is:
'Failed to connect, return code 1'
I then moved on and tried the NodeJs version https://github.com/GoogleCloudPlatform/nodejs-docs-samples/tree/master/iot/mqtt_example
Using the same roots.pem, private and public keys, the NodeJs example works perfectly. I can view the incoming messages on Google Console.
Is there any tools available to help me debug what the issue is with the C example? Or any suggestions on what the problem could be?
Thanks,
A

Answer 1

There is a wide range of reasons to why this could be happening, including unsupported versions. The Documentation for Cloud IoT provides some steps that you should verify first, but since you connected from the NodeJS code, we can discard some suggestions. What you could do to check errors is to use gcloud:
gcloud iot devices describe DEVICE_ID --project=PROJECT_ID --region=REGION --registry=REGISTRY_ID
The devices describe command may show additional error messages that can be used to help debug, including to verify that your device's credentials are not expired. Although some errors may not show up, my impression is that bad username or password errors would appear.