Update:

I am using the gazebo plugin from http://gazebosim.org/wiki/Tutorials/1.9/ROS_Control_with_Gazebo which gives the ability to send position commands via the command line. It is this code (libgazeboroscontrol.so) that I think should be processing the commands form rqt-plot.

rostopic pub /rrbot/joint1_position_controller/command std_msgs/Float64 "data: 1.5"

I can print the node/topic graph and it shows Gazebo as subscribing to this topic. But when I issue it via the terminal, rostopic never returns and the model does not move. Also if I try issuing this command via rqt-gui publish plugin. I can see the command being published but not processed. How I can debug this further to locate the problem.

The screen shot shows that Gazebo is waiting on /rrbot/joint1_position_controller/command [unknown type] however it is not possible to pass valid float values via rqt-plot this way. The data extension is needed but Gazebo considers this a separate topic.

note: the node is gazebo and it is using libgazeboroscontrol.so I have no user plugins in this environment.

viki:~$ rosnode info gazebo
--------------------------------------------------------------------------------
Node [/gazebo]
Publications: 
 * /rrbot/camera1/camera_info [sensor_msgs/CameraInfo]
 * /rrbot/laser/scan [sensor_msgs/LaserScan]
 * /rrbot/joint1_position_controller/pid/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /rrbot/joint1_position_controller/state [control_msgs/JointControllerState]
 * /rrbot/joint2_position_controller/state [control_msgs/JointControllerState]
 * /rrbot/joint2_position_controller/pid/parameter_updates [dynamic_reconfigure/Config]
 * /rrbot/joint2_position_controller/pid/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /rrbot/joint1_position_controller/pid/parameter_updates [dynamic_reconfigure/Config]
 * /gazebo/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /rosout [rosgraph_msgs/Log]
 * /rrbot/camera1/image_raw [sensor_msgs/Image]
 * /rrbot/camera1/parameter_updates [dynamic_reconfigure/Config]
 * /gazebo/link_states [gazebo_msgs/LinkStates]
 * /gazebo/model_states [gazebo_msgs/ModelStates]
 * /clock [rosgraph_msgs/Clock]
 * /rrbot/camera1/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /gazebo/parameter_updates [dynamic_reconfigure/Config]

Subscriptions: 
 * /gazebo/set_model_state [unknown type]
 * /gazebo/set_link_state [unknown type]
 * /clock [rosgraph_msgs/Clock]
 * /rrbot/joint1_position_controller/command [unknown type]
 * /rrbot/joint2_position_controller/command [unknown type]