marlin(ramps 1.4) with esp32 serial communication HELP

hello i am sinan,
I have a idea guys but i am stuck with serial communication with esp32.
Here is the idea; i am gonna use esp32 to send gcode to marlin based on ramps 1.4 with arduino mega, if i can make it happen then i will use bluetooth low energy to be sent gcodes to esp32 and esp32 sends them to ramps.
i am not building 3d printer, the reason i use marlin is that it supports tmc drivers, every single detail is done except serial communication between esp32 and ramps 1.4.
is there anyone who can help me.
thanks in advance

Very very vague

You need to implement serial protocol at it simplest form send gcodes, wait for OK. But you can also add line numbers and checksums so transmission errors can be detected
Full details are in [reprap.org]
[reprap.org]

I connect esp32 with aux 1 and level shifted rx pin. Then i wrote basic code for esp32 which is ;
#define rxd2
#define txd2
Void setup(){
Serial.begin(115200);
Serial2.begin(115200,SERIAL_8N1,rxd2,txd2);

}
Void loop(){

if(Serial.available()){
Serial.println(Serial2.readString());
}
}
After that i opened serial port and sent some command, nothing happened, am i missing something ?

GCODE must be uppercase by default
and lines must be terminated with LF