Bad Data : Arduino Mega & NodeMCU Serial Communication Currently I am working on an Arduino project. The project required to establish communication between Arduino Mega and NodeMCU ESP8266. Here are some details about the project:


NodeMCU Rx Pin is connected to Arduino Mega Pin 14 (Tx3), while NodeMCU Tx Pin is connected to Arduino Mega Pin 15 (Rx3), Jumper Wires is used to connect NodeMCU and Arduino Mega
Both Arduino Mega and NodeMCU are using baud rate 115200


Code for NodeMCU ESP8266 (Send The Data to Arduino Mega):

void loop(){
       esp.println("0000");

       esp.flush();
}


Code for Arduino Mega (Receive Data) : 

 if(Serial3.available()){

  data = Serial3.readStringUntil('\n');

  Serial3.flush();

  Serial.println(data);

}


The result : 


The intented and expected result is "0000", however, the result shown in serial monitor is not accurate. Anyone could advise?
Sir mane ardunio mega 2560 my programing k hy jo k different sensor k value lake display karty hy aur sir ab my us value ko server jo k thingspeak hy aus p bajna chahta ho sir aus k leye mane esp8266 node-mcu use kar raha ho to sir ab my chahta ho k arduino value lake node-mcu ko send kary aur node mcu phr server p sir in k leye serial communication chahyae between two arduino sir is k leye koi refrence or any help