Can't get sonar range from Gazebo model.

edit

I am trying to use rospy to get the range from a Gazebo sonar model.

rosdistro: kinetic
rosversion: 1.12.13
gazebo version: 7.12.0

This is the rospy program to get the range.

#!/usr/bin/env python
import sys
import rospy
from sensor_msgs.msg import Range 

rospy.init_node("robot_sonar", anonymous=True)

def callback(msg):
    print "Message = ", msg.range

sub_sonar1 = rospy.Subscriber("/sonar1", Range, callback)

r = rospy.Rate(10) # 10hz
while not rospy.is_shutdown():
   print "Waiting"
  r.sleep()

This is the Gazebo model for the sonar

  <link name='link'>
    <pose frame=''>0.2 0 0.2 0 -0 0</pose>
    <gravity>0</gravity>
    <sensor name='sonar1' type='sonar'>
      <pose frame=''>0.2 0 0 0 1.5707 3</pose>
      <sonar>
        <min>0</min>
        <max>10</max>
        <radius>0.3</radius>           
      </sonar>

      <always_on>1</always_on>
      <update_rate>30</update_rate>
      <visualize>1</visualize>
      <topic>sensor_msgs/Range</topic>
    </sensor>
    <self_collide>0</self_collide>
    <inertial>
      <inertia>
        <ixx>1</ixx>
        <ixy>0</ixy>
        <ixz>0</ixz>
        <iyy>1</iyy>
        <iyz>0</iyz>
        <izz>1</izz>
      </inertia>
      <mass>1</mass>
    </inertial>
    <kinematic>0</kinematic>
  </link>

I think the Gazebo model is not publishing the range topic correctly which I think must be set up correctly to publish the range to rospy. The Gazebo model has topic tags in the XML and below is some of the parameters I tried.

<topic>Range</topic>
<topic>sonar/Range</topic>
<topic>sensor_msgs/Range</topic>

Edit 1: Added rostopic list

/clock
/gazebo/link_states
/gazebo/model_states
/gazebo/parameter_descriptions
/gazebo/parameter_updates
/gazebo/set_link_state
/gazebo/set_model_state
/gazebo_gui/parameter_descriptions
/gazebo_gui/parameter_updates
/robot_sonar/cmd_vel
/robot_sonar/odom
/rosout
/rosout_agg
/tf