ESP32 (ESP-WROOM-32) as an MQTT Client Subscribed to Linux Server Load Average Messages
Here we go....
Preface:
Quote:
Rant: After a "very interesting" experience back-and-forth with Blynk yesterday over their "pull money out of your pocket for every tiny widget" business model when I was publishing a quick public service app to help folks in China regarding the Wuhan coronavirus, in also combination with the Blynk "terms of service" which permits Blynk to share all of a user's network data, every message, all user mined behavioral analytical "raw material" and share that data with any and all third parties; I decided to build my own messaging network to test these ESP32.......
..... so in a galaxy far, far, far away from commercial, data sharing corporations.....
For this project, I used the ESP-WROOM-32 as an MQTT (publish / subscribe) client which receives Linux server "load averages" as messages published as MQTT pub/sub messages. Here is the Arduino IDE code I wrote for the MQTT client running on the ESP32:
Code:
/*****************************************************************
* ESP32 (ESP-WROOM-32) MQTT Client Test v0.1
* The ESP32 subscribes to MQTT messages from an MQTT server
* published by a Linux server. In this example, server load
* average messages. The MQTT server requires username and password
* for basic authentication security.
*
* Neo www.unix.com v0.1 2 Feb 2020
* You are free to use this code anyway imaginable
* for your ESP32 MQTT projects.
*****************************************************************/
#include <WiFi.h>
#include <PubSubClient.h>
#define BAUD_RATE 115200
#define DEBUG false
const char *ssid = "YOUR_WIFI_SSID";
const char *password = "YOUR_WIFI_PASSWORD";
const char *mqttServer = "YOUR_MQTT_SERVER";
const int mqttPort = 1883; // YOUR_MQTT_PORT
const char *mqttUser = "YOUR_MQTT_SERVER_USER"; // Basic user and password authentication
const char *mqttPassword = YOUR_MQTT_SERVER_USER_PASSWORD "; // Basic user and password authentication
const int lengthTopic = 16; //required for the if-elseif message decoding based on topic
WiFiClient espClient;
PubSubClient client(espClient);
// The code below is self documenting, I think
void callback(char *topic, byte *payload, unsigned int length)
{
float loadvar, loadvar0, loadvar5, loadvar15;
if (DEBUG)
{
Serial.print("Message arrived in topic: ");
Serial.println(topic);
Serial.print("Message: ");
}
String w;
String receivedTopic = String(topic);
if (DEBUG)
{
int len = receivedTopic.length();
Serial.print("Length :");
Serial.println(String(len));
}
for (int i = 0; i < length; i++)
{
w = w + String((char)payload[i]);
}
if (receivedTopic.indexOf("loads/l1") > 0 and receivedTopic.length() < lengthTopic)
{
loadvar0 = w.toFloat();
Serial.printf("LOAD 1 ... %s \n", w);
}
else if (receivedTopic.indexOf("loads/l5") > 0 and receivedTopic.length() < lengthTopic)
{
loadvar0 = w.toFloat();
Serial.printf("LOAD 5 ... %s \n", w);
}
else if (receivedTopic.indexOf("loads/l15") > 0)
{
loadvar0 = w.toFloat();
Serial.printf("LOAD 15 ... %s \n", w);
}
else
{
loadvar = w.toFloat();
Serial.printf("Message: %s \n", w);
}
if (DEBUG)
{
Serial.println("-----------------------");
}
}
void setup()
{
Serial.begin(BAUD_RATE);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED)
{
delay(500);
Serial.printf("Connecting to WiFi: %s \n", ssid);
}
Serial.printf("Connected to the WiFi network: %s \n", ssid);
client.setServer(mqttServer, mqttPort);
client.setCallback(callback);
while (!client.connected())
{
Serial.printf("Connecting to MQTT Server: %s:%d\n", mqttServer, mqttPort);
if (client.connect("ESP32Client", mqttUser, mqttPassword))
{
Serial.println("Connected!");
}
else
{
Serial.print("failed with state ");
Serial.print(client.state());
delay(2000);
}
}
client.subscribe("server/loads");
client.subscribe("server/loads/l1");
client.subscribe("server/loads/l5");
client.subscribe("server/loads/l15");
}
void loop()
{
client.loop();
}
So far, no joy in finding a good IOS app for the iPhone to display this data in a nice dashboard.
I did find an OK "MQTT Terminal App" for the iPhone and I did confirm I can subscribe to these messages with MQTT on the iPhone. Unfortunately, all the "pretty dashboard apps for MQTT" I tried in the app store has some problems and none worked well "out of the box". However, the simple MQTT terminal apps work fine (but are not "pretty")
The MQTT terminal app I tested, which managed to work, does not add line breaks at the end of a message, and when I tried to send line breaks over MQTT, the clients stopped receiving the messages, which is expected since these pub/sub client/servers are not really meant for formatted data. Maybe I'm missing something small?
Hello,
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02-02-2020
