Turns out it was my flask server.
since I was running it in debug mode on the werkzeug wsgi server.
The connection reset issue was coming from the server.
turns out there is a well known 'Connection reset by peer' problem in python.
once I switched to a production server like waitress(windows ...

this code is probably missing variable declarations

String server_address;

bool is_config = false;

const byte interruptPin = 27;
volatile int interruptCounter = 0;
int numberOfInterrupts = 0;

portMUX_TYPE mux = portMUX_INITIALIZER_UNLOCKED;

void IRAM_ATTR handleInterrupt() {
static unsigned ...