Ensketon TTN Bridge

app.js

// Required packages.
var ttn = require("ttn");
var request = require('request');

// Global variables.
var appID = "appId"; // The App ID from TTN
var accessKey = "accessKey"; // The Access Key for that app
var hostname = "hostname"; // The hostname and port for the database server API.
var alreadyRegistered = []; // A list of already registered device ID's.

// Authenticate with TTN
ttn.data(appID, accessKey)
    .then(function (client) {
        // Display a message if connection was successfull.
        client.on("connect", function () {
            console.log("Connected to TTN.")
        });
        // Register a handler to fire when an uplink message is received.
        client.on("uplink", function (devID, payload) {
            console.log("Received uplink from", devID);
            // Dispatch the payload for analysis and further action.
            postToServer(devID, payload);
        });
    })
    // If something goes wrong, display what went wrong.
    .catch(function (error) {
        console.log("[ error    ]", error.toString());
    });

// The logic for bridging an uplink message to the database server.
function postToServer(devID, payload) {
    // Convert hexadecimal device UID to integer.
    devID = "2" + String(parseInt("0x" + devID));

    // Unpack the payload. Analyse what kind of payload it is, and extract values.
    // Stores values in the 'payload' variable.
    payload = unpackPayload(payload);

    // If the payload type is not recognized, display to payload text.
    if (payload[0] == null) {
        console.log("[  error  ] Unknown message:", payload[1].payload_raw.toString());
        return;
    } else if (payload[0] == "location") {
        if (alreadyRegistered.indexOf(devID) == -1) {
            console.log("[ new dev  ] New device:", devID)
            alreadyRegistered.push(devID)
            var createPayload = payload.slice();
            createPayload[0] = "register";
            makeRequest(devID, createPayload);
        }
    }

    // Dispatch the API request.
    makeRequest(devID, payload);
}

// The logic for unpacking the payload.
function unpackPayload(payload) {
    // Match sensor measurements. Example: 74 31 39 2E 33 31 68 37 36 2E 33 36 77 30 2E 32 35
    var values_regex = /t([0-9\-\.]+)h([0-9\-\.]+)w([0-9\-\.]+)/;
    // See if the payload text matches the format for a measurement message.
    // This also already fills the 'values' variable with the matched measurements.
    // Gotta love them regexes.
    var values = payload.payload_raw.toString().match(values_regex);
    if (values != null) {
        // Extract the time so we can reformat it to the right format.
        var time_regex = /([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2}):([0-9]{2})(?:.*)/;
        var time = payload.metadata.time.match(time_regex);
        var time_str = time[1] + "-" + time[2] + "-" + time[3] + ":" + time[4] + ":" + time[5] + ":" + time[6];
        // Display all extracted values.
        console.log("[ measure  ] Temp:", parseFloat(values[1]), "Hum:", parseFloat(values[2]), "Wind:", parseFloat(values[3]), "Time:", time_str);
        // Return the measurements and indicate the type of message.
        return ["measurement", parseFloat(values[1]), parseFloat(values[2]), parseFloat(values[3]), time_str];
    }

    // Match location. Example: 4C 35 32 2E 32 33 39 36 6C 36 2E 38 35 37 30
    var values_regex = /L([0-9\-\.]+)l([0-9\-\.]+)/;
    // This is mostly the same as the sensor measurement. See above for comments.
    var values = payload.payload_raw.toString().match(values_regex);
    if (values != null) {
        var time_regex = /([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2}):([0-9]{2})(?:.*)/;
        var time = payload.metadata.time.match(time_regex);
        var time_str = time[1] + "-" + time[2] + "-" + time[3] + ":" + time[4] + ":" + time[5] + ":" + time[6];
        console.log("[ location ] Latitude:", parseFloat(values[1]), "Longtitude:", parseFloat(values[2]), "Time:", time_str);
        return ["location", parseFloat(values[1]), parseFloat(values[2])];
    }

    // Unknown message.
    return [null, payload];
}

// The logic for constructing the URL based on the values.
function constructUrl(deviceID, values) {
    // We have multiple types of URL, the first value is the payload type.
    switch (values[0]) {
        // Construct the measurement URL. Replace dots with commas.
        case "measurement":
            return "http://" + hostname + "/prod/registermeasurement/" + deviceID + "/2" +
                "/3/" + String(values[1]).replace(".", ",") +
                "/4/" + String(values[2]).replace(".", ",") +
                "/5/" + String(values[3]).replace(".", ",") +
                "/" + values[4];
        // Construct the location URL. Replace dots with commas.
        case "location":
            return "http://" + hostname + "/prod/updatelocation/" + deviceID + "/2" +
                "/" + String(values[1]).replace(".", ",") +
                "/" + String(values[2]).replace(".", ",") +
                "/100";
        // Construct new device URL. Replace dots with commas.
        case "register":
            return "http://" + hostname + "/prod/registersensorsystem/" + deviceID + "/2" +
                "/" + String(values[1]).replace(".", ",") +
                "/" + String(values[2]).replace(".", ",") +
                "/100";
    }
}

// The logic for making a web request.
function makeRequest(devID, payload) {

    // If payload unpacking was successfull, construct the URL based on the values extracted from the payload.
    var url = constructUrl(devID, payload);
    console.log("[ http/get ]", url);

    // POST the values to the database server.
    request.post(url, function (error, response, body) {
        // If something goes wrong, let us know. Also let us know when it succeeds.
        console.log("[ http/res ]", (error !== null ? error.toString() : response.statusCode));
        console.log("Request to database server complete.");
    });

}

package.json

{
  "name": "ensketon-bridge",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./app.js"
  },
  "dependencies": {
    "ttn": "~2.3.1",
    "request": "~2.81.0"
  }
}