In this project you’ll create a standalone web server with a Raspberry Pi that can toggle two LEDs from an ESP8266 using MQTT protocol. You can replace those LEDs with any output (like a relay that controls a lamp).
In order to create the web server you will be using a Python microframework called Flask. Here’s the high level overview of the system:
Recommended resources:
- You need a Raspberry Pi board – read Best Raspberry Pi Starter Kits
- Raspberry Pi Web Server using Flask to Control GPIOs
- Testing Mosquitto Broker and Client on Raspbbery Pi
- How to Install Mosquitto Broker on Raspberry Pi
- What is MQTT and How It Works
- Getting Started with Node-RED on Raspberry Pi
.
Basic Raspberry Pi Setup
Before you continue reading this project, please make sure you have Raspbian Operating System installed in your Raspberry Pi.
You can read my Getting Started with the Raspberry Pi Guide to install Raspbian and complete the basic setup.
Run and install Mosquitto broker
The Raspberry Pi is going to interact with the ESP8266 with the MQTT protocol. Having Mosquitto broker installed, you need to have Mosquitto broker running on the background:
pi@raspberry:~ $ mosquitto -d
Python web server with Flask
We’re going to use a Python microframework called Flask to turn the Raspberry Pi into web server.
To install Flask, you’ll need to have pip installed. Run the following commands to update your Pi and install pip:
pi@raspberrypi ~ $ sudo apt-get update pi@raspberrypi ~ $ sudo apt-get upgrade pi@raspberrypi ~ $ sudo apt-get install python-pip python-flask
Then, you use pip to install Flask and its dependencies:
pi@raspberrypi ~ $ sudo pip install flask
Installing Python Paho-MQTT
The Paho-MQTT package provides a client class which enable applications to connect to an MQTT broker to publish messages, and to subscribe to topics and receive published messages. In this example, the Python web server is going to publish messages to the ESP8266 to turn the GPIOs on and off.
To install paho-mqtt run the following command:
pi@raspberrypi ~ $ sudo pip install paho-mqtt
Creating the Python Script
This is the core script of our application. It sets up the web server and when these buttons are pressed it publishes an MQTT message to the ESP8266.
To keep everything organized, start by creating a new folder:
pi@raspberrypi ~ $ mkdir web-server
pi@raspberrypi ~ $ cd web-server
pi@raspberrypi:~/web-server $
Create a new file called app.py.
pi@raspberrypi:~/web-server $ nano app.py
Copy and paste the following script to your Raspberry Pi
Gnd_To_Vcc
import paho.mqtt.client as mqtt
from flask import Flask, render_template, request
app = Flask(__name__)
mqttc=mqtt.Client()
mqttc.connect("localhost",1883,60)
mqttc.loop_start()
# Create a dictionary called pins to store the pin number, name, and pin state:
pins = {
4 : {'name' : 'GPIO 4', 'board' : 'esp8266', 'topic' : 'esp8266/4', 'state' : 'False'},
5 : {'name' : 'GPIO 5', 'board' : 'esp8266', 'topic' : 'esp8266/5', 'state' : 'False'}
}
# Put the pin dictionary into the template data dictionary:
templateData = {
'pins' : pins
}
@app.route("/")
def main():
# Pass the template data into the template main.html and return it to the user
return render_template('main.html', **templateData)
# The function below is executed when someone requests a URL with the pin number and action in it:
@app.route("/<board>/<changePin>/<action>")
def action(board, changePin, action):
# Convert the pin from the URL into an integer:
changePin = int(changePin)
# Get the device name for the pin being changed:
devicePin = pins[changePin]['name']
# If the action part of the URL is "on," execute the code indented below:
if action == "1" and board == 'esp8266':
mqttc.publish(pins[changePin]['topic'],"1")
pins[changePin]['state'] = 'True'
if action == "0" and board == 'esp8266':
mqttc.publish(pins[changePin]['topic'],"0")
pins[changePin]['state'] = 'False'
# Along with the pin dictionary, put the message into the template data dictionary:
templateData = {
'pins' : pins
}
return render_template('main.html', **templateData)
if __name__ == "__main__":
app.run(host='0.0.0.0', port=8181, debug=True)
Creating the HTML File
Keeping HTML tags separated from your Python script is how you keep your project organized.
Flask uses a template engine called Jinja2 that you can use to send dynamic data from your Python script to your HTML file.
Create a new folder called templates:
pi@raspberrypi:~/web-server $ mkdir templates pi@raspberrypi:~/web-server $ cd templates pi@raspberrypi:~/web-server/templates $
Create a new file called main.html.
pi@raspberrypi:~/web-server/templates $ nano main.html
Copy and paste the following template to your Pi:
<!DOCTYPE html>
<head>
<title>RPi Web Server</title>
<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">
<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap-theme.min.css" integrity="sha384-fLW2N01lMqjakBkx3l/M9EahuwpSfeNvV63J5ezn3uZzapT0u7EYsXMjQV+0En5r" crossorigin="anonymous">
<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" crossorigin="anonymous"></script>
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<h1>RPi Web Server - ESP8266 MQTT</h1>
{% for pin in pins %}
<h2>{{ pins[pin].name }}
{% if pins[pin].state == 'True' %}
is currently <strong>on</strong></h2><div class="row"><div class="col-md-2">
<a href="/esp8266/{{pin}}/0" class="btn btn-block btn-lg btn-default" role="button">Turn off</a></div></div>
{% else %}
is currently <strong>off</strong></h2><div class="row"><div class="col-md-2">
<a href="/esp8266/{{pin}}/1" class="btn btn-block btn-lg btn-primary" role="button">Turn on</a></div></div>
{% endif %}
{% endfor %}
</body>
</html>
Programming the ESP8266
For the ESP8266 to interact with the Raspberry Pi web server, you need to install PubSubClient library. This library provides a client for doing simple publish/subscribe messaging with a server that supports MQTT (basically allows your ESP8266 to talk with Python web server).
Installing the Library
1) Click here to download the PubSubClient library. You should have a .zip folder in your Downloads folder
2) Unzip the .zip folder and you should get pubsubclient-master folder
3) Rename your folder from pubsubclient-master to pubsubclient
4) Move the pubsubclient folder to your Arduino IDE installation libraries folder
5) Then, re-open your Arduino IDE
The library comes with a number of example sketches. See File > Examples > PubSubClient within the Arduino IDE software.
Uploading sketch
Finally, you can upload the full sketch to your ESP8266 (replace with your SSID, password and RPi IP address):
<pre class="wp-block-syntaxhighlighter-code">/*****
All the resources for this project:
<blockquote class="wp-embedded-content" data-secret="edrICub03B"><a href="https://randomnerdtutorials.com/">Home</a></blockquote><iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="position: absolute; clip: rect(1px, 1px, 1px, 1px);" title="“Home” — Random Nerd Tutorials" src="https://randomnerdtutorials.com/embed/#?secret=edrICub03B" data-secret="edrICub03B" width="600" height="338" frameborder="0" marginwidth="0" marginheight="0" scrolling="no"></iframe>
*****/
// Loading the ESP8266WiFi library and the PubSubClient library
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
// Change the credentials below, so your ESP8266 connects to your router
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";
// Change the variable to your Raspberry Pi IP address, so it connects to your MQTT broker
const char* mqtt_server = "YOUR_RPi_IP_Address";
// Initializes the espClient
WiFiClient espClient;
PubSubClient client(espClient);
// Connect an LED to each GPIO of your ESP8266
const int ledGPIO5 = 5;
const int ledGPIO4 = 4;
// Don't change the function below. This functions connects your ESP8266 to your router
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.print("WiFi connected - ESP IP address: ");
Serial.println(WiFi.localIP());
}
// This functions is executed when some device publishes a message to a topic that your ESP8266 is subscribed to
// Change the function below to add logic to your program, so when a device publishes a message to a topic that
// your ESP8266 is subscribed you can actually do something
void callback(String topic, byte* message, unsigned int length) {
Serial.print("Message arrived on topic: ");
Serial.print(topic);
Serial.print(". Message: ");
String messageTemp;
for (int i = 0; i < length; i++) {
Serial.print((char)message[i]);
messageTemp += (char)message[i];
}
Serial.println();
// Feel free to add more if statements to control more GPIOs with MQTT
// If a message is received on the topic home/office/esp1/gpio2, you check if the message is either 1 or 0. Turns the ESP GPIO according to the message
if(topic=="esp8266/4"){
Serial.print("Changing GPIO 4 to ");
if(messageTemp == "1"){
digitalWrite(ledGPIO4, HIGH);
Serial.print("On");
}
else if(messageTemp == "0"){
digitalWrite(ledGPIO4, LOW);
Serial.print("Off");
}
}
if(topic=="esp8266/5"){
Serial.print("Changing GPIO 5 to ");
if(messageTemp == "1"){
digitalWrite(ledGPIO5, HIGH);
Serial.print("On");
}
else if(messageTemp == "0"){
digitalWrite(ledGPIO5, LOW);
Serial.print("Off");
}
}
Serial.println();
}
// This functions reconnects your ESP8266 to your MQTT broker
// Change the function below if you want to subscribe to more topics with your ESP8266
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Attempt to connect
/*
YOU NEED TO CHANGE THIS NEXT LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS
To change the ESP device ID, you will have to give a unique name to the ESP8266.
Here's how it looks like now:
if (client.connect("ESP8266Client")) {
If you want more devices connected to the MQTT broker, you can do it like this:
if (client.connect("ESPOffice")) {
Then, for the other ESP:
if (client.connect("ESPGarage")) {
That should solve your MQTT multiple connections problem
THE SECTION IN loop() function should match your device name
*/
if (client.connect("ESP8266Client")) {
Serial.println("connected");
// Subscribe or resubscribe to a topic
// You can subscribe to more topics (to control more LEDs in this example)
client.subscribe("esp8266/4");
client.subscribe("esp8266/5");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
// The setup function sets your ESP GPIOs to Outputs, starts the serial communication at a baud rate of 115200
// Sets your mqtt broker and sets the callback function
// The callback function is what receives messages and actually controls the LEDs
void setup() {
pinMode(ledGPIO4, OUTPUT);
pinMode(ledGPIO5, OUTPUT);
Serial.begin(115200);
setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
}
// For this project, you don't need to change anything in the loop function.
// Basically it ensures that you ESP is connected to your broker
void loop() {
if (!client.connected()) {
reconnect();
}
if(!client.loop())
/*
YOU NEED TO CHANGE THIS NEXT LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS
To change the ESP device ID, you will have to give a unique name to the ESP8266.
Here's how it looks like now:
client.connect("ESP8266Client");
If you want more devices connected to the MQTT broker, you can do it like this:
client.connect("ESPOffice");
Then, for the other ESP:
client.connect("ESPGarage");
That should solve your MQTT multiple connections problem
THE SECTION IN recionnect() function should match your device name
*/
client.connect("ESP8266Client");
}
</pre>
Schematics
The schematics for this project are very straightforward. Simply connect two LEDs with two resistors to your ESP8266 as shown in the figure below.
Launching the Web Server
To launch your Raspberry Pi web server move to the folder that contains the file app.py:
pi@raspberrypi:~/web-server/templates $ cd ..
Then, run the following command:
pi@raspberrypi:~/web-server $ sudo python app.py
Your web server should start immediately on port :8181!
Demonstration
Open your Raspberry Pi address in your browser by entering its IP address, in my case: http://192.168.1.98:8181
Note: you must enter your IP address followed by :8181
Wrapping up
In the next blog post, we will publish sensor readings with the ESP8266 to the Python web server.
Thanks for reading.
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