How to make the plugin publish a topic

[Juan Alvarez Fernandez]

Hello,

I`m starting with the gazebo and ros controller. My problem is that I would like to load the pioneer2dx and control it. I want to add the plugin to move the robot in the sdf file: https://bitbucket.org/osrf/gazebo_models/src/65b3e70c198ba414960295c065b17c8b8fee2eec/pioneer2dx/model.sdf?at=default 

I read the tutorials, but I don`t understand, because it see many file formats: xml, xacro ... and all files within the same folder.

Do I have to build the urdf from sdf? Do gazebo have any Topic that I can use?

I just want to move the robot in gazebo simulation with the command line or script in python. 

I would like the robot to publish a topic, but I don`t know how. I tried to change the file this way:

<plugin filename="libDiffDrivePlugin.so" name="diff_drive">
  <left_joint>left_wheel_hinge</left_joint>
  <right_joint>right_wheel_hinge</right_joint>
  <topicName> /pioneer2/movimiento </topicName>
  <torque>5</torque>
</plugin>

But it doesn't work. I would really appreciate any tips.

I have installed ros-indigo, gazebo 2 and the package gazebo_ros.

Thank you!

Note: Sorry for my English.