Connecting to Azure IoT Central

Squirrel Code
1

Hi, I’m trying to connect to the Azure IoT Central vía DPS. This snippet of code retrieved from the Dev Center works great:

#require "AzureIoTHub.agent.lib.nut:5.1.0"

const AZURE_IOT_CENTRAL_SCOPE_ID = "<YOUR_AZURE_IOT_CENTRAL_SCOPE_ID>";
const AZURE_IOT_CENTRAL_DEVICE_ID = "<YOUR_AZURE_IOT_CENTRAL_DEVICE_ID>";
const AZURE_IOT_CENTRAL_GROUP_KEY = "<YOUR_AZURE_IOT_CENTRAL_GROUP_KEY>";
local AZURE_IOT_CENTRAL_DEVICE_KEY = http.base64encode(crypto.hmacsha256(AZURE_IOT_CENTRAL_DEVICE_ID, http.base64decode(AZURE_IOT_CENTRAL_GROUP_KEY)));

local client = null;
dps <- AzureIoTHub.DPS(AZURE_IOT_CENTRAL_SCOPE_ID, AZURE_IOT_CENTRAL_DEVICE_ID, AZURE_IOT_CENTRAL_DEVICE_KEY);

function onConnected(err) {
    if (err != 0) {
        server.error("Connection failed: " + err);
    }
}

local registrationCalled = false;
local onCompleted = function(err, resp, connStr) {
    if (err == 0) {
        server.log(registrationCalled ? "Device has been registered" : "Device is registered already");
        ::client <- AzureIoTHub.Client(connStr, onConnected);
    } else if (err == AZURE_DPS_ERROR_NOT_REGISTERED && !registrationCalled) {
        // The device is not registered
        server.log("Device is not registered. Starting registration...");
        registrationCalled = true;

        // Register the device
        dps.register(onCompleted);
    } else {
        server.error("Error occurred: code = " + err + ", response = " + http.jsonencode(resp));
    }
}.bindenv(this);

// Try to get a Device Connection String
dps.getConnectionString(onCompleted);

And I get the following message on the logger:

2021-07-14T19:04:27.825 +00:00	[Agent]	Device is registered already

But, when I attempt to connect to the Azure IoT Central with this code (notice that I only added one line at the bottom from the last code):

#require "AzureIoTHub.agent.lib.nut:5.1.0"

const AZURE_IOT_CENTRAL_SCOPE_ID = "<YOUR_AZURE_IOT_CENTRAL_SCOPE_ID>";
const AZURE_IOT_CENTRAL_DEVICE_ID = "<YOUR_AZURE_IOT_CENTRAL_DEVICE_ID>";
const AZURE_IOT_CENTRAL_GROUP_KEY = "<YOUR_AZURE_IOT_CENTRAL_GROUP_KEY>";
local AZURE_IOT_CENTRAL_DEVICE_KEY = http.base64encode(crypto.hmacsha256(AZURE_IOT_CENTRAL_DEVICE_ID, http.base64decode(AZURE_IOT_CENTRAL_GROUP_KEY)));

local client = null;
dps <- AzureIoTHub.DPS(AZURE_IOT_CENTRAL_SCOPE_ID, AZURE_IOT_CENTRAL_DEVICE_ID, AZURE_IOT_CENTRAL_DEVICE_KEY);

function onConnected(err) {
    if (err != 0) {
        server.error("Connection failed: " + err);
    }
}

local registrationCalled = false;
local onCompleted = function(err, resp, connStr) {
    if (err == 0) {
        server.log(registrationCalled ? "Device has been registered" : "Device is registered already");
        ::client <- AzureIoTHub.Client(connStr, onConnected);
    } else if (err == AZURE_DPS_ERROR_NOT_REGISTERED && !registrationCalled) {
        // The device is not registered
        server.log("Device is not registered. Starting registration...");
        registrationCalled = true;

        // Register the device
        dps.register(onCompleted);
    } else {
        server.error("Error occurred: code = " + err + ", response = " + http.jsonencode(resp));
    }
}.bindenv(this);

// Try to get a Device Connection String
dps.getConnectionString(onCompleted);
client.connect();

I get the following error:

2021-07-14T19:05:50.175 +00:00	[Agent]	ERROR: the index 'connect' does not exist
2021-07-14T19:05:50.175 +00:00	[Agent]	ERROR:   in main agent_code:36

What’s the problem? :disappointed_relieved:

PD: I think that is something related to Squirrel, I don’t have too much experience with this programming language.

2

client is only instantiated when onCompleted is called. Maybe try calling client.connect() from inside onCompleted?

3

Same problem when is inside of onCompleted, but inside of onConnected it works. However, since client is a global variable, why can’t I use it outside of those functions?

4

Ah - client is not a global variable. It’s a local defined in the main context, but as soon as your program runs off the end of your code, it’ll be deleted.

If you change:
local client = null
to
client <- null

…then it’s a global and will persist.

5

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