Azure Function to publish a message to my local MQTT broker via Azure IoT Hub

index.js

var Client = require('azure-iothub').Client;
var Message = require('azure-iot-common').Message;

function printResultFor(op) {
    return function printResult(context, err, res) {
        context.log('printResult for ' + op);
        if (err) context.log(op + ' error: ' + err.toString());
        if (res) context.log(op + ' status: ' + res.constructor.name);
        if (err) {
            context.res = {
                status: 500,
                body: op + ' error: ' + err.toString()
            };
        }
        else {
            context.res = {
                status: 200,
                body: "OK"
            };
        }
        context.done();
    };
}

module.exports = function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.', JSON.stringify(req, null, 2));

    var topic = null;
    var message = null;

    if (req.query.topic) {
        topic = req.query.topic;
    }
    if (req.body && req.body.topic) {
        topic = req.body.topic;        
    }
    if (req.query.message) {
        message = req.query.message;
    }
    if (req.body && req.body.message) {
        message = req.body.message;        
    }
    
    if (req.query.ping || (req.body && req.body.ping)) {
        context.res = {
            // status: 200, /* Defaults to 200 */
            body: "PING OK"
        };
    }
    else if (topic && message) {
        context.res = {
            // status: 200, /* Defaults to 200 */
            body: "OK"
        };
    }
    else {
        context.res = {
            status: 400,
            body: "Please pass a topic and message on the query string or in the request body"
        };
    }

    if (topic && message) {
        var connectionString = 'HostName=<My IoT Hub>.azure-devices.net;SharedAccessKeyName=service;SharedAccessKey=<key>';
        var targetDevice = 'MyMQTTBroker';

        var serviceClient = Client.fromConnectionString(connectionString);

        serviceClient.open(function (err) {
            if (err) {
                context.log('Could not connect: ' + err.message);
                context.done();
            } else {
                context.log('Service client connected');
                var m = {
                    "topic": topic,
                    "message": message
                };
                var msg = new Message(JSON.stringify(m));
                msg.ack = 'full';
                msg.messageId = "My Message ID";
                context.log('Sending message: ' + msg.getData());
                serviceClient.send(targetDevice, msg, printResultFor('send').bind(null, context));
            }
        });
    }
    else {
        context.done();
    }
};