So I am very new to gazebo, working on my first project. So far my program spawns robots randomly in a given area. I want to be able to control them via a ROS node. Since Im using Pioneer2dx models, I am trying to use the diff drive plugin. I have spent literally days trying to find relevant information online, to no avail. I have also posted multiple forum questions on here and got answers that either didn't work or weren't useful to me. Here's what I REALLY need to know:

1. How to access the diff drive plugin from my code (what is the #include).

2. What functions do I need to use to get the robot to move in the simulation

3. How to link this plugin to my pioneer2dx model in the world file.

Please help! thanks in advance. . .

UPDATE

Here is my world file:

<sdf version="1.5"> <world name="default"> <include> <uri>model://sun</uri> </include>

    <!-- A ground plane -->
    <include>
        <uri>model://ground_plane</uri>
    </include>

    <!-- Generate Population -->
    <population name="pioneer_population1">
        <!-- Define the population model type -->
        <model name="pioneer1">
            <include>
                <static>false</static>
                <uri>model://pioneer2dx</uri>
            </include>
            <!-- <plugin name="pioneer_prog" filename="libpioneer_prog.so"/> -->
            <plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
                        <alwaysOn>true</alwaysOn>
                        <updateRate>10</updateRate>
                            <leftJoint>left_wheel_hinge</leftJoint>
                        <rightJoint>right_wheel_hinge</rightJoint>
                        <wheelSeparation>0.5380</wheelSeparation>
                        <wheelDiameter>0.2410</wheelDiameter>
                        <torque>20</torque>
                        <commandTopic>cmd_vel</commandTopic>
                    <odometryTopic>odom</odometryTopic>
                        <odometryFrame>odom</odometryFrame>
                        <robotBaseFrame>base_footprint</robotBaseFrame> 
                        <robotNamespace>gz</robotNamespace> 
             </plugin> 
        </model>

        <!-- Center spawn around (0,0,0) with orientation <0,0,0> -->
        <pose>0 0 0 0 0 0</pose>

        <!-- Size of spawn area -->
        <box>
            <size>8 8 0.01</size>
        </box>

        <!-- world_builder will insert this line based on user params -->
        <!-- MODEL_COUNT -->

        <!-- /MODEL_COUNT -->

        <!-- Define how the models will be distributed -->
        <!-- Distribution types: random, uniform, grid, linear-x, 
        liner-y, linear-z -->
        <distribution>
            <type>random</type>
        </distribution>
    </population>
</world>

</sdf>

I get this error when i try to open the world file:

Launching simulator. . .done
Warning [parser.cc:437] Converting a deprecated SDF source[data-string].
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
Couldn't find an AF_INET address for []
^CCouldn't find an AF_INET address for []

why would my world file be giving me an error to do with ros::init()?

UPDATE 2

As it turns out, the ros::init() error was caused by problems with my CMakeLists.txt file in my gazebo plugin directory. My file structure is the same as that used in the gazebo plugin tutorials. I needed to add these lines to CMakeLists.txt in order to include any ROS headers into my gazebo plugin:

find_package(roscpp ... (more)