#include <Servo.h>

Servo myservo; // create servo object to control a servo
char receivedPos;

void setup() {
 Serial.begin(9600);
 myservo.attach(9); // attaches the servo on pin 9 to the servo object
 myservo.write(0); // on power on, move servo to central position
 Serial.println("1: moves to absolute position 0 dregrees");
 Serial.println("2: moves to absolute position 45 dregrees");
 Serial.println("3: moves to absolute position 90 dregrees");
 Serial.println("4: moves to absolute position 135 dregrees");
 Serial.println("5: moves to absolute position 180 dregrees");
}

void loop() {
 while(Serial.available()) {
  String commands = Serial.readString(); // read the incoming data as string
  Serial.println("I read string: "+ commands); // feedback of data received
  receivedPos = commands.charAt(0); // convert to char to enable Switch Statement use
  switch (receivedPos) {
   case '1': myservo.write(0); break;
   case '2': myservo.write(45); break;
   case '3': myservo.write(90); break;
   case '4': myservo.write(135); break;
   case '5': myservo.write(180); break;
   default: break;
  }
 }
}