while(1)
Completely unnecessary. You're already in an infinite loop, you don't need to do another one.
Serial.println("Enter servo angle: ");
if (Serial.available() > 0) { // check for serial input
int angle = Serial.read(); // read the incoming byte:
myservo1.write(angle); // tell servo to go to position in variable 'pos'
Serial.print("I received: ");
Serial.println(angle);
}
}
You're receiving ASCII characters from the serial monitor. '9' is not the same as 9.