I resolve my problem on delayed respond by changing
This is from the visual studio side
port.Write('\n'+"my command")
to
port.WriteLine("my command")
this is to satisfy the below script from arduino side
void loop() {
if (Serial.available() > 0) { // something came across serial
integerValue = 0; // throw away previous integerValue
while(1) { // force into a loop until 'n' is received
incomingByte = Serial.read();
if (incomingByte == '\n') break; // exit the while(1), we're done receiving
if (incomingByte == -1) continue; // if no characters are in the buffer read() returns -1
integerValue *= 10; // shift left 1 decimal place
// convert ASCII to integer, add, and shift left 1 decimal place
integerValue = ((incomingByte - 48) + integerValue);
}
Serial.println(integerValue);
}
}