Code on Node

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <SoftwareSerial.h>
#include <String.h>
SoftwareSerial fromUno(D5,D6); // (Rx, Tx)

char* ssid = "B";
char* password =  "A";
const char* mqttServer = "Z";
const int mqttPort = 1;
const char* mqttUser = "Y";
const char* mqttPassword = "X;

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {

  Serial.begin(9600);
  fromUno.begin(115200);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
  }

  Serial.println("Connected to the WiFi network");

  client.setServer(mqttServer, mqttPort);

  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");

    if (client.connect("ESP32Client", mqttUser, mqttPassword )) {

      Serial.println("connected");

    } else {

      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);

    }
  }
}

void loop() {
   char json[100];
   json[0] = fromUno.read();
   String json2 = "{\"planta\":{\"umidade\":200,\"criticidade\":1}}";

  Serial.println("Sending message to MQTT topic..");

  if (client.publish("test", json2) == true) {
    Serial.println("Success sending message");
  } else {
    Serial.println("Error sending message");
  }

  client.loop();
  Serial.println("-------------");

  delay(10000);
}