Deserialization Error rosserial

edit

HI i'm trying to create a subscriber and a publisher on my Arduino IDE to subscribe to the following message:

# Steering Wheel
float32 steering_wheel_angle_cmd        # rad, range -9.6 to 9.6
float32 steering_wheel_angle_velocity   # rad/s, range 0 to 17.5, 0 = maximum
float32 steering_wheel_torque_cmd       # Nm, range -8.0 to 8.0
uint8 cmd_type

How ever getting the following error when i run

rosrun rosserial_python serial_node.py /dev/ttyACM0

Error:

[INFO] [1581828495.528782]: ROS Serial Python Node
[INFO] [1581828495.542420]: Connecting to /dev/ttyACM0 at 57600 baud
[INFO] [1581828498.162551]: Note: publish buffer size is 280 bytes
[INFO] [1581828498.163540]: Setup publisher on my_topic [dbw_mkz_msgs/SteeringCmd]

[INFO] [1581828498.171809]: Note: subscribe buffer size is 280 bytes
[INFO] [1581828498.172683]: Setup subscriber on /vehicle/steering_cmd [dbw_mkz_msgs/SteeringCmd]
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/rosserial_python/serial_node.py", line 89, in <module>
    client.run()
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rosserial_python/SerialClient.py", line 504, in run
    self.callbacks[topic_id](msg)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rosserial_python/SerialClient.py", line 107, in handlePacket
    m.deserialize(data)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/dbw_mkz_msgs/msg/_SteeringCmd.py", line 133, in deserialize
    raise genpy.DeserializationError(e) #most likely buffer underfill
genpy.message.DeserializationError: unpack requires a string argument of length 18

The following is my code on Arduino IDE

#include <ros.h>
#include <dbw_mkz_msgs/SteeringCmd.h>
#include <std_msgs/Float64.h>
#include <std_msgs/Float32.h>

ros::NodeHandle nh;

dbw_mkz_msgs::SteeringCmd msg;

void messageCb(const dbw_mkz_msgs::SteeringCmd& msg1){

  msg.steering_wheel_angle_cmd= msg1.steering_wheel_angle_cmd;

  digitalWrite(13, HIGH-digitalRead(13));  }

ros::Subscriber<dbw_mkz_msgs::SteeringCmd> sub("/vehicle/steering_cmd", &messageCb );

ros::Publisher p("my_topic", &msg);

void setup()
{ 
  pinMode(13, OUTPUT);
  nh.initNode();
  nh.subscribe(sub);

  nh.advertise(p);
}

void loop()
{      
  p.publish(&msg );

  nh.spinOnce();


  delay(1000);}