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mqtt-ciotc

README.md

Message Queue Telemetry Transport (MQTT) client for Google Cloud IoT Core

This sample app demonstrates connecting to Google Cloud IoT Core and publishing a single message.

Building

To build the sample, you must first download, build, and install the following projects:

After you have installed all the dependencies, you can build the sample as:

gcc mqtt_ciotc.c -lssl -lcrypto -lpaho-mqtt3cs -ljwt -ljansson -o mqtt_ciotc

or by invoking make, specifying OPENSSL_DIR, pointiing to the OpenSSL library.

Due to conflicting libraries existing on your build machine, you may need to specify the library paths, for example, if you installed the dependencies in $HOME/code, you could do the following to help the linker find the correct libraries:

gcc mqtt_ciotc.c -L$HOME/code/openssl -lssl -lcrypto -lpaho-mqtt3cs -L$HOME/code/libjwt -ljwt -ljansson -o mqtt_ciotc

For simplifying the build process, a Docker image is provided that generates the build configuration. After installing Docker, build the image with:

docker build -t your-docker-tag -f docker/Dockerfile .

It will take a little while for the Docker image to build. After the Docker image is built, you can access the builder as:

docker run -t -i your-docker-tag /bin/bash

Running

After you have successfully built the sample, you are almost ready to run the sample.

  1. Setup your libraries:

    export LD_LIBRARY_PATH=/usr/local/lib export LD_RUN_PATH=/usr/local/lib

  2. Browse to the sample folder

    cd mqtt-ciotc

  3. Create a Cloud Pub/Sub topic gcloud pubsub topics create

  4. Setup the Cloud IOT environment ./setup_device.sh --registry-name
    --registry-region <e.g. us-central1>
    --device-id
    --telemetry-topic <Your telemetry Cloud Pub/Sub topic>

  5. Run the sample ./mqtt_ciotc
    --deviceid
    --region <e.g. us-central1>
    --registryid
    --projectid
    --keypath <e.g. ./ec_private.pem>
    --algorithm <e.g. RS256> --rootpath <e.g. ./roots.pem>

You must provide the deviceid, registryid, and projectid parameters as they are used in calculating the client ID used for connecting to the MQTT bridge. The ecpath parameter should point to your private EC key created when you registered your device. The rootpath parameter specifies the roots.pem file that can be downloaded from https://pki.google.com/roots.pem. For example:

wget https://pki.google.com/roots.pem

The following example demonstrates usage of the sample if my device ID is my-device, registry ID is my-registry, and project ID is blue-ocean-123.

mqtt_ciotc "Hello world!" --deviceid my-device --registryid my-registry \
    --projectid blue-ocean-123 --keypath ./rsa_private.pem --algorithm RS256 \
     --rootpath ./roots.pem --region us-central1