mqtt checker node

check_mqtt_server.js

#!/usr/bin/env node
/*
 * Check an mqtt server by doing a pub/sub
 *
 * Author: Dave Eddy <dave@daveeddy.com>
 * Date: July 13, 2018
 * License: MIT
 */

var getopt = require('posix-getopt');
var mqtt = require('mqtt');

function usage() {
    console.log('Usage: check_mqtt_server <-t topic> <-S url> [-k] [-U username] [-P password]');
}

var parser = new getopt.BasicParser([
    'U:(username)',
    'P:(password)',
    'S:(server)',
    'k(insecure)',
    't:(topic)'
].join(''), process.argv);

var topic;
var url;
var opts = {
    clientId: 'nagios-check_mqtt_server'
};
var option;
while ((option = parser.getopt()) !== undefined) {
    switch (option.option) {
    case 'S':
        url = option.optarg;
        break;
    case 'U':
        opts.username = option.optarg;
        break;
    case 'P':
        opts.password = option.optarg;
        break;
    case 'h':
        usage();
        process.exit(0);
        break;
    case 'k':
        opts.rejectUnauthorized = false;
        break;
    case 't':
        topic = option.optarg;
        break;
    default:
        usage();
        process.exit(1);
        break;
    }
}

if (!url || !topic) {
    console.log('unknown: -t <topic> and -S <server> required');
    process.exit(3);
}

var randomString = Math.random().toString();
var code = 0;

var client = mqtt.connect(url, opts);

client.on('connect', function () {
    client.subscribe(topic);
    client.publish(topic, randomString);
});

client.on('message', function (_topic, payload) {
    var message = payload.toString();

    if (_topic !== topic) {
        // client library malfunction?
        console.log('critical: got topic "%s" expected "%s"', _topic, topic);
        code = 2;
    } else if (message !== randomString) {
        console.log('critical: got message "%s" on topic %s expected "%s"',
            message, topic, randomString);
        code = 2;
    } else {
        console.log('ok: mqtt server pub/sub working');
        code = 0;
    }

    client.end();
});

client.on('error', function (err) {
    console.log('critical: mqtt server error - %s', err.message);
    code = 2;
});

client.on('close', function () {
    process.exit(code);
});