Smartphone Controlled Arduino Bot

int lm1=3,lm2=5;
int rm1=9,rm2=6;
int command=0;
int PWMSpeed=200;




void setup() {
  Serial.begin(9600);
  pinMode(lm1,OUTPUT);
  pinMode(lm2,OUTPUT);
  pinMode(rm1,OUTPUT);
  pinMode(rm2,OUTPUT);

  motor_off();

}

void loop() {
    if(Serial.available() > 0)
    {
      command = Serial.read();
      Serial.println(command);
    if(command == '2')
    {
      forward();
    } 
    else if(command == '1')
    {
      backward();
    } 
    else if(command == '3')
    {
      right(); 
    } 
    else if(command == '4')
    {
      left();
    } 
    else if(command == '0')
    {
      motor_off();        
    } 
    else 
    {
      motor_off();
    }
   }
}



void motor_off() 
{
  Serial.print("Motor :  STOP\n");
  digitalWrite(lm1, LOW);
  digitalWrite(lm2, LOW);

  digitalWrite(rm1, LOW);
  digitalWrite(rm2, LOW);
}

void right() 
{
  Serial.print("Motor :  LEFT\n");
  analogWrite(lm1, PWMSpeed);
  digitalWrite(lm2, LOW);

  analogWrite(rm1, PWMSpeed);
  digitalWrite(rm2, LOW);

}

void left() 
{
  Serial.print("Motor :  RIGHT\n");
  digitalWrite(lm1, LOW);
  analogWrite(lm2, PWMSpeed);

  digitalWrite(rm1, LOW);
  analogWrite(rm2, PWMSpeed);

}

void forward() 
{
  Serial.print("Motor :  FORWARD\n");
  digitalWrite(lm1, LOW);
  digitalWrite(lm2, HIGH);

  digitalWrite(rm1, HIGH);
  digitalWrite(rm2, LOW);
}

void backward() 
{
  Serial.print("Motor :  BACK\n");
  digitalWrite(lm1, HIGH);
  digitalWrite(lm2, LOW);

  digitalWrite(rm1, LOW);
  digitalWrite(rm2, HIGH);
}