Communication

1. Overview

Communication controllers allows sharing data between a Python application running on the robot ('server code'), and an external application that uses the RESTful API ('client code').

Let’s imagine an application where you show a screen asking from the user to choose which object the robot should pick. Once the user makes a choice, you need to send that data to the Python app, that is in charge of looking for that object, sending the robot to the position of that object and picking it.
Of course that you can create a local server and handle the entire communication. But it can be much faster and easy with this controller.

Let’s examine the following diagram:

1. On our server code we are creating a listener that will be triggered when client side will send a message.
2. On the client side, after the user selects an object, we are sending a message with the relevant data using our Restful API endpoint.
3. This listener on our server code is being triggered, we read the data and get the selected object and continue with the business logic of the application.

This flow works also when we want to send a message from the server code to the client code.
In that case, we will create a listener on our client code, and send a message from the server code using send_msg() function.

2. Using the controller

Creating the controller in your app:

from raya.application_base import RayaApplicationBase

class RayaApplication(RayaApplicationBase):
    async def setup(self):
        ...
        self.comm = self.enable_controller('communication')
        ...

The controller class includes two methods to communicate:

• mqtt_publish_message()
• mqtt_create_subscription()
• mqtt_remove_subscription()

3. Examples

• Communication to Server
• Communication to Client