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my publisher node

#!/usr/bin/env python
# license removed for brevity
import rospy
from ros_tutorials_topic.msg import IoTSensor
import random

#create a new publisher. we specify the topic name, then type of message then the queue size
pub = rospy.Publisher('iot_sensor_topic', IoTSensor, queue_size=10)

#we need to initialize the node
rospy.init_node('iot_sensor_publisher_node', anonymous=True)

#set the loop rate
rate = rospy.Rate(1) # 1hz
#keep publishing until a Ctrl-C is pressed
i = 0
while not rospy.is_shutdown():
    iot_sensor = IoTSensor()
    iot_sensor.id = 1
    iot_sensor.name="iot_parking_01"
    iot_sensor.temperature = 24.33 + (random.random()*2)
    iot_sensor.humidity = 33.41+ (random.random()*2)
    rospy.loginfo("I publish:")
    rospy.loginfo(iot_sensor)
    pub.publish(iot_sensor)
    rate.sleep()
    i=i+1

subscriber nopde

#!/usr/bin/env python
import rospy
from ros_tutorials_topic.msg import IoTSensor

def iot_sensor_callback(iot_sensor_message):
    rospy.loginfo("new IoT data received: (%d, %s, %.2f ,%.2f)", 
        iot_sensor_message.id,iot_sensor_message.name,
        iot_sensor_message.temperature,iot_sensor_message.humidity)

rospy.init_node('iot_sensor_subscriber_node', anonymous=True)

rospy.Subscriber("iot_sensor_topic", IoTSensor, iot_sensor_callback)

# spin() simply keeps python from exiting until this node is stopped
rospy.spin()

cmakelist file

cmake_minimum_required(VERSION 2.8.3)
project(ros_tutorials_topic)

## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  message_generation
  roscpp
  rospy
  std_msgs
)

## System dependencies are found with CMake's conventions
# find_package(Boost REQUIRED COMPONENTS system)


## Uncomment this if the package has a setup.py. This macro ensures
## modules and global scripts declared therein get installed
## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

################################################
## Declare ROS messages, services and actions ##
################################################

## To declare and build messages, services or actions from within this
## package, follow these steps:
## * Let MSG_DEP_SET be the set of packages whose message types you use in
##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).
## * In the file package.xml:
##   * add a build_depend tag for "message_generation"
##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET
##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in
##     but can be declared for certainty nonetheless:
##     * add a exec_depend tag for "message_runtime"
## * In this file (CMakeLists.txt):
##   * add "message_generation" and every package in MSG_DEP_SET to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * add "message_runtime" and every package in MSG_DEP_SET to
##     catkin_package(CATKIN_DEPENDS ...)
##   * uncomment the add_*_files sections below as needed
##     and list every .msg/.srv/.action file to be processed
##   * uncomment the generate_messages entry below
##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)

## Generate messages in the 'msg' folder
 add_message_files(
   FILES
   IoTSensor.msg
 )

## Generate services in the 'srv' folder
# add_service_files(
#   FILES
#   Service1.srv
#   Service2.srv
# )

## Generate actions in the 'action' folder
# add_action_files(
#   FILES
#   Action1.action
#   Action2.action
# )

## Generate added messages and services with any dependencies listed here
 generate_messages(
   DEPENDENCIES
   std_msgs
 )

################################################
## Declare ROS dynamic reconfigure parameters ##
################################################

## To declare and build dynamic reconfigure parameters within this
## package, follow these steps:
## * In the file package.xml:
##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"
## * In this file (CMakeLists.txt ...