How can i run Dc motor & servo motor ..?(ROS,Arduino)

edit

Hi guys I'm making a autonomous RC car .(using ROS(odroid),arduino) But, I can't run dc motor and servo motor.

This is my arduino code.

const int motorpin=10;
const int servopin=11;

Servo servo;

class data {
  public :
  float servo_cmd
  float motor_cmd
};

data cmd_data;
ros::NodeHandle nh;

void servo_cb(const std_msgs::Float32& servo){
  servo.write(servo.data);
}


void motor_cb(const std_msgs::Float32& motor){
 analogWrite(motorpin,motor.data);
}

std_msgs::Float32 servo_cmd;
std_msgs::Float32 motor_cmd;
ros::Subscriber<std_msgs::Float32>ordtoard_servo("servo",servo_cb);
ros::Subscriber<std_msgs::Float32>ordtoard_motor("motor",motor_cb);

void setup() {
pinMode(motorpin,OUTPUT);
servo.attach(servopin);


nh.initNode();
  nh.subscribe(ordtoard_servo);
  nh.subscribe(ordtoard_motor);
}

void loop(){
}

why cannot i run this code..?