example: Add HTTP to MQTT bridge

It was used along luftdaten sensor, using custom API using endpoint:

    /mqtt/broker.hivemq.com/1883/luftdaten.info,sensors,0

    mosquitto_sub -v -h broker.hivemq.com -p 1883 -t luftdaten.info,sensors,0
    {... ,"sensordatavalues":[{ ... "value":"42.00" ...

If needed replace broker/port, with your sensorid (not 0):

https://meine.luftdaten.info/sensors# (# : it's a number)

Note that for now only IoT.js runtime is supported in this example.

Relate-to: opendata-stuttgart/sensors-software#33
Change-Id: I8b75cc0311a5dac4c05b697ea32c17a1e3f18a60
Signed-off-by: Philippe Coval <p.coval@samsung.com>

example/server-mqtt.js

@@ -0,0 +1,86 @@
+/* -*- mode: js; js-indent-level:2;  -*-
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright 2018-present Samsung Electronics France SAS, and other contributors
+ *
+ * This Source Code Form is subject to the terms of the MIT Licence
+ * If a copy of the MIT was not distributed with this file
+ * You can obtain one at:
+ * https://spdx.org/licenses/MIT.html
+ */
+
+var console = require('console');
+// Disable logs here by editing to '!console.log'
+var verbose = !console.log || function () {};
+
+var Express = null;
+try {
+  Express = require('../iotjs-express');
+} catch (err) {
+  Express = require('iotjs-express');
+}
+
+var mqtt = require('mqtt');
+
+function publish(options, topic, message) {
+  if (typeof message === 'object') {
+    message = JSON.stringify(message);
+  }
+  this.client = new mqtt.connect(options, function () {
+    this.publish(topic, message);
+    verbose(message);
+  });
+}
+
+function App() {
+  var http = require('http');
+  var port = 8888;
+  if (process.argv[2]) {
+    port = Number(process.argv[2]);
+  }
+  var app = new Express();
+  var self = http.createServer(app.request);
+  console.log('Listening on:\nhttp://localhost:' + port);
+
+  app.get('/.well-known/security.txt', function(req, res) {
+    return res.end('Contact: https://www.npmjs.com/~rzr\n');
+  });
+
+  app.get('/', function(req, res) {
+    res.json({Usage: '/mqtt/:host/:port/:topic/:message'});
+  });
+
+  app.get('/mqtt/:host/:port/:topic/:message', function(req, res) {
+    publish({
+      host: req.params.host,
+      port: Number(req.params.port)
+    }, req.params.topic, req.params.message);
+
+    return res.json({topic: req.params.topic});
+  });
+
+  app.post('/mqtt/:host/:port/:topic', function(req, res) {
+    publish({
+      host: req.params.host,
+      port: Number(req.params.port)
+    }, req.params.topic, req.body);
+
+    return res.json({topic: req.params.topic});
+  });
+
+  app.put('/mqtt/:host/:port/:topic', function(req, res) {
+    publish({
+      host: req.params.host,
+      port: Number(req.params.port)
+    }, req.params.topic, req.body);
+
+    return res.json({topic: req.params.topic});
+  });
+
+  self.listen(port);
+}
+
+// Main App
+if (module.parent === null) {
+  App();
+}