Unity-Robotics-Hub/tutorials/ros_unity_integration/subscriber.md

ROS–Unity Integration: Subscriber

Create a simple Unity scene which subscribes to a ROS topic to change the colour of a GameObject.

NOTE: If following from Publisher tutorial proceed to Setting Up Unity Scene step.

Setting Up ROS

(You can skip this if you already did the ROS–Unity Integration Publisher tutorial.)

• Copy the tutorials/ros_packages/robotics_demo folder of this repo into the src folder in your Catkin workspace.

• Follow the ROS–Unity Initial Setup guide.

• Open a new terminal window, navigate to your Catkin workspace, and run the following commands:

   source devel/setup.bash
   rosrun robotics_demo server_endpoint.py
  

Once the server_endpoint has started, it will print something similar to [INFO] [1603488341.950794]: Starting server on 192.168.50.149:10000.

Setting Up Unity Scene

• Generate the C# code for UnityColor message by going to RosMessageGeneration -> AutoGenerateMessages -> Single Message...
• Set the input file path to PATH/TO/Unity-Robotics-Hub/tutorials/ros_packages/robotics_demo/msg/UnityColor.msg and click GENERATE!
  • The generated file will be saved in the default directory Assets/RosMessages/msg
• Create a script and name it RosSubscriberExample.cs
• Paste the following code into RosSubscriberExample.cs
  • Note Script can be found at tutorials/ros_unity_integration/unity_scripts

using System.Net.Sockets;
using System.Threading.Tasks;
using UnityEngine;
using RosColor = RosMessageTypes.RoboticsDemo.UnityColor;

public class RosSubscriberExample : RosSubscriber
{
    public GameObject cube;

    protected override async Task HandleConnectionAsync(TcpClient tcpClient)
    {
        await Task.Yield();

        using (var networkStream = tcpClient.GetStream())
        {
            RosColor colorMessage = (RosColor)ReadMessage(networkStream, new RosColor());
            Debug.Log("Color(" + colorMessage.r + ", "+ colorMessage.g + ", "+ colorMessage.b + ", "+ colorMessage.a +")");
            cube.GetComponent<Renderer>().material.color = new Color32((byte)colorMessage.r, (byte)colorMessage.g, (byte)colorMessage.b, (byte)colorMessage.a);
        }
    }

    void Start()
    {
        StartMessageServer();
    }

}

• Create an empty GameObject and name it RosSubscriber
• Attach the RosSubscriberExample script to the RosSubscriber GameObject and drag the cube GameObject onto the cube parameter in the Inspector window.
• In the Inspector window of the Editor change the unityHostName parameter on the RosSubscriber GameObject to the Unity machine's URI. (Note for Windows users: the connection will be rejected unless you put the actual IP address ROS is connecting to. That's not necessarily the same as your machine's main IP address.)
• Press play in the editor

In ROS Terminal Window

• After the scene has entered Play mode, run the following command: rosrun robotics_demo color_publisher.py to change the color of the cube GameObject in Unity to a random color

Continue to the ROS–Unity Integration Service.