Arduino Data on MQTT

#include <SPI.h>
#include <PubSubClient.h>
#include <WiFiNINA.h>
#include <ArduinoJson.h>

#include "arduino_secrets.h"

///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID;     // your network SSID (name)
char pass[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)

char host[] = "mqtt.akenza.io";
char clientid[] = "Arduino";
char username[] = "0783ddd64683f579";
char password[] = "bd604gmgit0x7kilc8puok3g2rxsldl2";
char outTopic[] = "/up/bd604gmgit0x7kilc8puok3g2rxsldl2/id/99E77F4ECC728656";

//set interval for sending messages (milliseconds)
const long interval = 8000;
unsigned long previousMillis = 0;

int count = 0;

//receive data
void callback(char* topic, byte* payload, unsigned int length) {

  char str[length+1];
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  int i=0;
  
  for (i=0;i<length;i++) {
    Serial.print((char)payload[i]);
    str[i]=(char)payload[i];
  }

  str[i] = 0; // Null termination
  Serial.println();
  
  StaticJsonDocument <256> doc;
  deserializeJson(doc,payload);

  // deserializeJson(doc,str); can use string instead of payload
  const char* sensor = doc["sensor"];
  long time          = doc["time"];
  float latitude    = doc["data"][0];
  float longitude   = doc["data"][1];

  Serial.println("latitude =");
  Serial.println(latitude,2);
  Serial.println(sensor);
  
}

WiFiClient wifiClient;
PubSubClient client(host, 1883, callback, wifiClient);

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // attempt to connect to Wifi network:
  Serial.print("Attempting to connect to WPA SSID: ");
  Serial.println(ssid);
  while (WiFi.begin(ssid, pass) != WL_CONNECTED) {
    // failed, retry
    Serial.print(".");
    delay(5000);
  }

  Serial.println("You're connected to the network");
  Serial.println();

  if (client.connect(host, username, password)) {
    Serial.print("Connected to ");
    Serial.println(host);
    Serial.println();
    
    boolean r = client.subscribe(outTopic);
    Serial.print("Subscribed to ");
    Serial.println(outTopic);
    Serial.println();
    } 
    else {
      // connection failed
      Serial.println("Connection failed ");
      Serial.println(client.state());
      Serial.println();
  }
}

void loop()
{
  StaticJsonDocument<256> doc;
  doc["Temperature"] = 22;
  doc["Humidity"] = 68;
  doc["Light"] = 96;

  // Add an array
  JsonArray data = doc.createNestedArray("data");
  data.add(48);
  data.add(2.3);
  
  char out[128];
  int b =serializeJson(doc, out);
  Serial.print("publishing bytes = ");
  Serial.println(b,DEC);
  
  boolean rc = client.publish(outTopic, out);
  
  // The above line prints:
  // {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}
  delay(5000);
  client.loop();
}