How to return the value in Arduino function (that can be read by the connected device)?

Question

Right now I have an RC car program for Arduino. The code is like this:

void loop() {
  distance = Dist.getDistanceCentimeter();
  if(distance<=5 & distance>1)
  if(Serial.available()) {
    lkf = Serial.read();
  switch(lkf) {
  case 'a':
     forward();
     servoX.write(90);
     lkf=0; 
     break;    
  }
}

I wrote a TCPclient that can order the RC car to move forward by connecting through TCP and sending the message "a" to the Arduino board.

The problem is how to return the distance to the cilent? Is it simply return distance; or something like system.println(distance);? Thanks for helping.

Answer 1

You are using the USB interface, right? So you just use Serial to send data back. For example, this would send the distance every second:

unsigned long lastSent;
void loop() {
  distance = Dist.getDistanceCentimeter();
  if (millis () - lastSent >= 1000)  // every second
  {
    lastSent = millis ();
    Serial.println (distance);
  }

  if (distance <= 5 & distance > 1)
  {
    if (Serial.available()) {
      command = Serial.read();
      switch (command) {
        case 'a':
          forward();
          servoX.write(90);
          command = 0;
          break;
      }  // end of switch
    }
  }
}