Episode 21: GUI-O push notification from any device

kl3m3n

This example shows how to create custom push notification on any Internet enabled device (WiFi, Ethernet) and send it to a targeted Android device.

NOTE: Push notifications are available in GUI-O PRO version only.

The code from this example can be combined with other GUI-O examples using MQTT, Classic Bluetooth or Low Energy Bluetooth. See https://www.gui-o.com/examples/gui-o-and-boards.

Software prerequisites:

Arduino IDE (https://www.arduino.cc/en/software)
Arduino source code (you can copy the source code from the snippet below, or download it here

/*
 * GUI-O Basic Push notification example
 *
 * Copyright (C) 2024, GUI-O Team
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */


#include <WiFiClientSecure.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>

static const char* ssid = "<ssid>"; // router name
static const char* pass = "<pass>"; // router password
static const char* appUuid = "<appUuid>"; // application uuid (retrieve from GUI-O app)
static const char* resource = "https://apis.gui-o.com:9501/gui-o/resources/api/sendPushNotification"; // request resource / endpoint

static const char* letsencrypt_ca = \
"-----BEGIN CERTIFICATE-----\n" \
"MIIFazCCA1OgAwIBAgIRAIIQz7DSQONZRGPgu2OCiwAwDQYJKoZIhvcNAQELBQAw\n" \
"TzELMAkGA1UEBhMCVVMxKTAnBgNVBAoTIEludGVybmV0IFNlY3VyaXR5IFJlc2Vh\n" \
"cmNoIEdyb3VwMRUwEwYDVQQDEwxJU1JHIFJvb3QgWDEwHhcNMTUwNjA0MTEwNDM4\n" \
"WhcNMzUwNjA0MTEwNDM4WjBPMQswCQYDVQQGEwJVUzEpMCcGA1UEChMgSW50ZXJu\n" \
"ZXQgU2VjdXJpdHkgUmVzZWFyY2ggR3JvdXAxFTATBgNVBAMTDElTUkcgUm9vdCBY\n" \
"MTCCAiIwDQYJKoZIhvcNAQEBBQADggIPADCCAgoCggIBAK3oJHP0FDfzm54rVygc\n" \
"h77ct984kIxuPOZXoHj3dcKi/vVqbvYATyjb3miGbESTtrFj/RQSa78f0uoxmyF+\n" \
"0TM8ukj13Xnfs7j/EvEhmkvBioZxaUpmZmyPfjxwv60pIgbz5MDmgK7iS4+3mX6U\n" \
"A5/TR5d8mUgjU+g4rk8Kb4Mu0UlXjIB0ttov0DiNewNwIRt18jA8+o+u3dpjq+sW\n" \
"T8KOEUt+zwvo/7V3LvSye0rgTBIlDHCNAymg4VMk7BPZ7hm/ELNKjD+Jo2FR3qyH\n" \
"B5T0Y3HsLuJvW5iB4YlcNHlsdu87kGJ55tukmi8mxdAQ4Q7e2RCOFvu396j3x+UC\n" \
"B5iPNgiV5+I3lg02dZ77DnKxHZu8A/lJBdiB3QW0KtZB6awBdpUKD9jf1b0SHzUv\n" \
"KBds0pjBqAlkd25HN7rOrFleaJ1/ctaJxQZBKT5ZPt0m9STJEadao0xAH0ahmbWn\n" \
"OlFuhjuefXKnEgV4We0+UXgVCwOPjdAvBbI+e0ocS3MFEvzG6uBQE3xDk3SzynTn\n" \
"jh8BCNAw1FtxNrQHusEwMFxIt4I7mKZ9YIqioymCzLq9gwQbooMDQaHWBfEbwrbw\n" \
"qHyGO0aoSCqI3Haadr8faqU9GY/rOPNk3sgrDQoo//fb4hVC1CLQJ13hef4Y53CI\n" \
"rU7m2Ys6xt0nUW7/vGT1M0NPAgMBAAGjQjBAMA4GA1UdDwEB/wQEAwIBBjAPBgNV\n" \
"HRMBAf8EBTADAQH/MB0GA1UdDgQWBBR5tFnme7bl5AFzgAiIyBpY9umbbjANBgkq\n" \
"hkiG9w0BAQsFAAOCAgEAVR9YqbyyqFDQDLHYGmkgJykIrGF1XIpu+ILlaS/V9lZL\n" \
"ubhzEFnTIZd+50xx+7LSYK05qAvqFyFWhfFQDlnrzuBZ6brJFe+GnY+EgPbk6ZGQ\n" \
"3BebYhtF8GaV0nxvwuo77x/Py9auJ/GpsMiu/X1+mvoiBOv/2X/qkSsisRcOj/KK\n" \
"NFtY2PwByVS5uCbMiogziUwthDyC3+6WVwW6LLv3xLfHTjuCvjHIInNzktHCgKQ5\n" \
"ORAzI4JMPJ+GslWYHb4phowim57iaztXOoJwTdwJx4nLCgdNbOhdjsnvzqvHu7Ur\n" \
"TkXWStAmzOVyyghqpZXjFaH3pO3JLF+l+/+sKAIuvtd7u+Nxe5AW0wdeRlN8NwdC\n" \
"jNPElpzVmbUq4JUagEiuTDkHzsxHpFKVK7q4+63SM1N95R1NbdWhscdCb+ZAJzVc\n" \
"oyi3B43njTOQ5yOf+1CceWxG1bQVs5ZufpsMljq4Ui0/1lvh+wjChP4kqKOJ2qxq\n" \
"4RgqsahDYVvTH9w7jXbyLeiNdd8XM2w9U/t7y0Ff/9yi0GE44Za4rF2LN9d11TPA\n" \
"mRGunUHBcnWEvgJBQl9nJEiU0Zsnvgc/ubhPgXRR4Xq37Z0j4r7g1SgEEzwxA57d\n" \
"emyPxgcYxn/eR44/KJ4EBs+lVDR3veyJm+kXQ99b21/+jh5Xos1AnX5iItreGCc=\n" \
"-----END CERTIFICATE-----\n";

// Connection and requests handling
WiFiClientSecure client;
HTTPClient http;

// Icoming data buffer
String in;

void setup() {
  // Debug output
  Serial.begin(115200);
  
  // Connect WiFi (keep trying...)
  Serial.print("Connecting to ");
  Serial.println(ssid);
  
  // Start WiFi
  WiFi.begin(ssid, pass);
  while(WiFi.status() != WL_CONNECTED) { 
    Serial.print(".");
    delay(500); 
  }

  // Set root CA
  client.setCACert(letsencrypt_ca);
  
  Serial.println("WiFi connected!");
}

void loop() {
  while(Serial.available()) {
    const char c = Serial.read();
    in += c;
  
    if(c == '\n') {
      // Send push notification
      sendPushNotification("GUI-O push notification example", in.c_str(), appUuid);
      // clear buffer
      in = "";
    }  
  }  
}

void sendPushNotification(const char* title, const char* message, const char* appUuid) {
  DynamicJsonDocument jsonPayload(512);
  jsonPayload["appUuid"] = String(appUuid);
  jsonPayload["messageTitle"] = String(title);
  jsonPayload["messageText"] = String(message);

  String payload;
  serializeJson(jsonPayload, payload);

  if (http.begin(client, resource)) {
      http.addHeader("Content-Type", "application/json");

      const int httpCode = http.POST(payload);

      if (httpCode == HTTP_CODE_OK) {
        String response = http.getString();
        Serial.print("Response: ");
        Serial.println(response);
      } 
      else {
        Serial.print("Request failed. Status code: ");
        Serial.println(httpCode);
      }

      http.end();
  }
}

GUI-O application (https://play.google.com/store/apps/details?id=com.guio.guioapp)

Hardware prerequisites:

Any Internet enabled board (WiFi, Ethernet) that is compatible with Arduino IDE

1. Retrieve application's universally unique identifier (UUID)

Open GUI-O application, navigate to settings and select "Info"
Verify that the text "Available" is displayed under "Push notifications" entry
Make a note of "Application UUID" (you can share the "Application UUID" by tapping on it)

2. Modify and upload the code

Open Arduino IDE
Select "File -> Open"
Navigate to location where BasicPushNotification.zip archive was extracted (if downloaded)
Select BasicPushNotification.ino and confirm
Set your router name and password
Set your "Application UUID" (retrieved in form the GUI-O app)
Make sure that your board is connected to your PC
Ensure that the correct port and baud rate are selected
Press upload button to start code upload

3. Send a push notification

Open any serial terminal and connect to your board (baud rate 115200)
Enter your push notification message on the serial terminal - the text must be terminated with the \n (new line) character.
Observe the response on the serial terminal - if successful, message "Push notification sent" will be displayed
Check the push notification on your Android device

NOTE: Customize the sound, vibration, LED light, and priority of GUI-O app notifications by navigating to "Android settings -> Apps -> Manage apps".

If you have any questions or run into any problems, please let me know!

Best regards,
kl3m3n