drive robot in gazebo ros with Clearpath Husky A200 or other robots

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Thank you ZdenekM for your answer and your help.

I would like to better understand how to run the code to drive my robot in Gazebo. At first, I have to launch Gazebo and then I have to add my robot model into the virtual worlds: but then? How I have to run my code from my shell?

Is there any possibility to easily and successfully run this code to virtually drive my robot under Gazebo? For example, I try to open USB port, but I do not think it will be possible if there is not real robot connect in my PC. Do I have to change something or Gazebo is able to emulate the USB port?

I have this simple testing code:

int main(int argc, char *argv[]) {
/* Configure the serial port */
const char* port = (argc == 2) ? argv[1] : "/dev/ttyUSB0";
clearpath::Transport::instance().configure(port, 3 /* max retries*/);

/* Get and print some system information */
clearpath::DataPlatformInfo *platform_info = clearpath::DataPlatformInfo::getUpdate();
cout << *platform_info << endl;
delete platform_info;
clearpath::DataPowerSystem  *power_info = clearpath::DataPowerSystem::getUpdate();
cout << *power_info << endl;
delete power_info;

cout << "Press enter to continue... ";
getchar();

/* Subscribe to some interesting data */
clearpath::DataSystemStatus::subscribe(1);
clearpath::DataEncoders::subscribe(5);
clearpath::DataSystemStatus * cur_status = NULL;
clearpath::DataEncoders * cur_encoders = NULL;

/* Ramp speed to 0.6m/s over 6 seconds.
 * We use the 1Hz system status message for timing, so we want to begin by
 * waiting for the first message, which is sent shortly after the beginning
 * of the subscription */
cur_status = clearpath::DataSystemStatus::waitNext();
cout << *cur_status << endl; 
delete cur_status;

for(int i=1; i<=6; ++i) {
    // Set motor speed
    clearpath::SetVelocity(0.1*i, 0.0, 0.5).send();

    /* While waiting for the next system status message to arrive, print
     * all encoder messages as they are received */
    while( ! (cur_status = clearpath::DataSystemStatus::popNext()) ) {

        if( (cur_encoders = clearpath::DataEncoders::popNext()) ) {
            cout << *cur_encoders << endl;
            delete cur_encoders;
        }
    }
    cout << *cur_status << endl;
    delete cur_status;
}

/* Terminate subscriptions */
clearpath::DataSystemStatus::subscribe(0xffff);
clearpath::DataEncoders::subscribe(0xffff);

return 0;

}