Testing the communication reliability | MATLAB IoT Analytics | Forum

One way you could do this is to change your local DNS server setting to something that cannot resolve api.thingspeak.com or thingspeak.com. You can also create a custom plugin that goes RED/GREEN if the device has not sent data to ThingSpeak within a certain time. Here’s an example:

Plugin HTML:

%%PLUGIN_CSS%%
%%PLUGIN_JAVASCRIPT%%

Plugin CSS:

body { background-color: #fff; }

.led-box {
height: 90%;
width: 100%;
margin-top: 30px;
float: left;
}

.led-box p {
text-align: center;
font-size: 25px;
margin: 1em;
}

.red-led {
margin: 0 auto;
width: 100px;
height: 100px;
background-color: #F00;
border-radius: 50%;
box-shadow: rgba(0, 0, 0, 0.2) 0 -1px 7px 1px, inset #441313 0 -1px 9px, rgba(255, 0, 0, 0.5) 0 2px 12px;
}

.green-led {
margin: 0 auto;
width: 70px;
height: 70px;
background-color: #0F0;
border-radius: 50%;
box-shadow: rgba(0, 0, 0, 0.2) 0 -1px 7px 1px, inset #304701 0 -1px 9px, #89FF00 0 2px 12px;
}

Plugin JavaScript:

https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js
https://www.google.com/jsapi

google.setOnLoadCallback(initChart);

// load the data
function loadData() {

// get the data from thingspeak
$.getJSON('https://api.thingspeak.com/channels/_CHANNEL_ID_/feed/last.json?api_key=READ_API_KEY', function(data) {

// get the data point
p = (Date.now() - new Date(data.created_at)) / (60*1000);
q = document.getElementById('LED');

// if there is a data point display it
if (p && q) {
if (p>3){ q.className = 'red-led'; } else {q.className = 'green-led';}
}
});
}

// initialize the chart
function initChart() {
loadData();
// load new data every 15 seconds
setInterval('loadData()', 15*1000);
}