Convert terminal command to messages/plugin

Hi there,

I'm trying to control a differential drive robot to follow a ball. I thought I could initialize a node with the ball and publish it's pose and initialize another node on the robot(pioneer2dx) to subscribe to it. After implementing this, further for controlling the robot, I don't know how to apply velocity to each wheel separately. From the terminal I could send instructions and control left and right wheel separately with the command **gz joint -m pioneer2dx -j right_wheel_hinge --vel-t 2**. How can I implement this by using messages or using plugins?

Thanks in advance