A basic pub/sub application to test the Google Cloud IoT Core and Pub/Sub services.

1. In the Google Cloud IoT Core page (GCP Console), click "Create device registry.";
2. Enter "registry_id" for the Registry ID;
3. Choose "us-central1" for the Cloud region;
4. Choose "MQTT" for the Protocol;
5. In the "Telemetry topic" dropdown list, select "Create a topic";
6. In the "Create a topic" dialog, enter "topic_name" in the Name field;
7. Click "Create" in the dialog;
8. Leave the Device state topic and Certificate value fields blank, since they are optional.
9. Click Create on the Cloud IoT Core page.

1. Click "Add device" on the Registry Details;
2. Enter "device_id" for the Device ID;
3. Select "Allow" for Device communication;
4. Since Authentication and Device metadata are optional, leave them blank or use default values;
5. Click Add.

1. To create an RSA256 key with 2048 bits, run the following command in the terminal (if you want to set your own information, just ommit the "-subj" param):

openssl req -x509 -newkey rsa:2048 -keyout rsa_private.pem -nodes \
-out rsa_cert.pem -subj "/CN=unused"

2. On the Device details page, for your created device, click "Add public key";
3. Choose Upload and select "RS256_X509". Search by your "rsa_cert.pem" file and select it;
4. Click Add.

• The GCP supports the MQTT protocol with a broker running on mqtt.googleapis.com:8883. The port 443 can also be used;

• Unfortunately, according to Google Cloud documentation: "the managed MQTT bridge run by Cloud IoT Core does not support all publish/subscribe operations, such as creating arbitrary topics that devices can use to send messages between them";

• To connect an MQTT client, the full device path must be specified:

  projects/{project-id}/locations/{cloud-region}/registries/{registry-id}/devices/{device-id}