Mobile Computing and Internet of Things 2020/21 fall

/*
* Connects to a WiFi network and MQTT broker, then publishes WiFi signal strength readings
*/

#include <WiFi.h>
#include <PubSubClient.h>
const char* ssid     = "your-ssid";
const char* password = "your-password";
const char* mqtt_server = "your_broker_ip";


WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);


long lastMsg = 0;


void setup() {
    Serial.begin(115200);
    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.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());

    // Set up MQTT
    mqttClient.setServer(mqtt_server, 1883);

}

void reconnect() {
  // Loop until we're reconnected
  while (!mqttClient.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP32Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (mqttClient.connect(clientId.c_str())) {
      Serial.println("Connected");
      // Connected - do something useful - subscribe to topics, publish messages, etc.
    } else {
      Serial.print("failed, rc=");
      Serial.print(mqttClient.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

int rssiVal = 0;
void loop() {
  if (!mqttClient.connected()) {
    reconnect();
  }

  mqttClient.loop();

  // Read a value
  long now = millis();
  if (now - lastMsg > 100) {
    lastMsg = now;

    rssiVal = WiFi.RSSI(); // wifi signal strength 
    mqttClient.publish("foo",  String(rssiVal).c_str());
    Serial.println(rssiVal);

  }
}