how to do Arduino to esp8266 communication

Question

I am trying to do Arduino to ESP8266 communication, but I am not able to send data to esp8266. However I can receive data from esp8266.

Here if my Arduino code:

#include <SoftwareSerial.h>
SoftwareSerial ESPserial(0, 1); // RX | TX

void setup()
{
  Serial.begin(115200);     // communication with the host computer
  // Start the software serial for communication with the ESP8266
  ESPserial.begin(9600);

  Serial.println("Enter 1 to turn led high & 2 to turn led low.");
}
// the loop function runs over and over again forever
void loop() {
  // listen for communication from the ESP8266 and then write it to the serial monitor
  if ( ESPserial.available() )   {
    Serial.write( ESPserial.read() );
  }

  // listen for user input and send it to the ESP8266
  if ( Serial.available() )       {
    ESPserial.write( Serial.read() );
  }

}

Here is esp8266 code:

void setup()
{
  Serial.begin(9600);     // communication with the host computer
  // Start the software serial for communication with the ESP8266
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
  Serial.println("ESP -- Hello");
  delay(1000);
  // listen for user input and send it to the ESP8266
  if ( Serial.available() )  {

    int ledState = Serial.parseInt();
    if (ledState == 1) {
      digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
      Serial.println("ESP Led On\n");
    }
    if (ledState == 2) {
      digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
      Serial.println("ESP Led Off\n");
    }
  }
}

Once I upload both sketches, then I can see it terminal " ESP -- Hello " keep printing comming from esp8266 but when I enter 1 or 2, its not sent to esp8266 due to which I never see "ESP led on/off" messages , so correct me guys what mistake I am making.

Answer 1

using SoftSerial on the hardware serial isn't working on Arduino properly as sometime data receive and sometime not with garbage added so Using digital pins other 2, & 3 other than hardware serial resolved the issue.