Request-response service best practice?

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Background

• New to ROS 1/2. Working with ROS2. Playing with Python.

• ROS2 is installed on PC and also cross-compiled and installed on embedded system.

  • PC: Kubuntu 16.04, just followed ROS2 instructions - got Ardent, also installed colcon
  • The embedded system is Elphel 393 camera system Xilinx Zynq (32bit ARM) based with GigE network. Yocto + meta-ros got ros2 recipes built fine.

• Demos AddTwoInts and Talker-Listener work fine in pc-camera, camera-pc

• There's a lighttpd webserver that is running on the camera and the parameters are normally changed with http requests like:

  wget http://ip/somescript.php?p1=v1&p2=v2
  

  The response is an xml status string with updated pars values:

  <pars>
    <p1>v1</p1>
    <p2>v2</p2>
  </pars>
  

• More Info (unrelated)

Question

Now I would like to implement a similar behavior (i.e. use a single service to send commands and get status replies as bools or preferably strings) in ROS2 - with a service. But after having a brief look into several repos (ros2_intel_realsense, axis_camera and inertial_sense_ros) - they don’t seem to use services and *.srv files a lot.

What did I miss? Is it implemented via parameters? What's the best practice?

Thanks.