Hi,
I’m going to code an application that receives commands from serial port (RS485) and then must interact with XProtect (as example changing a view in smart client). Is better work with Component or Plug-in?
I think the key here is that you want to change view in the Smart Client, hearing this I would go for a Smart Client plugin.
You can also have a standalone application or service that could signal a Smart Client plugin. You might be able to do without a plugin if you can use Matrix for the cameras you need to show. If a Smart Client plugin is needed it could as well pick up the serial communication.
Hearing of data coming in on serial port makes me think of XProtect Transact. See - https://www.milestonesys.com/solutions/hardware-and-add-ons/milestone-addons/transact/ Maybe it fits, maybe it is nothing like what you seek..
I hope I have not confused the subject. If I should make a clearer recommendation I think I would need to know more about the scenario, you are welcome to ask again with further information..