# ROS–Unity Integration: Service Create a simple Unity scene which calls a [ROS service](http://wiki.ros.org/Services) with a GameObject's position and rotation to receive a new position to move the GameObject towards. ## Setting Up ROS (Skip to [Start the Position service](service.md#start-the-position-service) if you already did the [ROS–Unity Integration Publisher](publisher.md) or [Subscriber](subscriber.md) tutorials.) - 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](setup.md) guide. - Open a new terminal window, navigate to your ROS workspace, and run the following commands: ```bash 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`. ## Start the Position service - Open a new terminal window, navigate to your ROS workspace, and run the following commands: ```bash source devel/setup.bash rosrun robotics_demo position_service.py ``` ## Setting Up Unity Scene - Generate the C# code for `PositionService`'s messages by going to `Robotics` -> `Generate ROS Messages...` - Set the input file path to `PATH/TO/Unity-Robotics-Hub/tutorials/ros_packages/robotics_demo`, expand the robotics_demo folder and click `Build 1 srv`. ![](images/generate_messages_2.png) - The generated files will be saved in the default directory `Assets/RosMessages/RoboticsDemo/srv`. - Create a script and name it `RosServiceExample.cs` - Paste the following code into `RosServiceExample.cs` - **Note:** This script can be found at `tutorials/ros_unity_integration/unity_scripts`. ```csharp using System; using RosMessageTypes.RoboticsDemo; using UnityEngine; using Debug = UnityEngine.Debug; public class RosServiceExample : MonoBehaviour { ROSConnection ros; public string serviceName = "pos_srv"; public GameObject cube; // Cube movement conditions public float delta = 1.0f; public float speed = 2.0f; private Vector3 destination; float awaitingResponseUntilTimestamp = -1; void Start() { ros = ROSConnection.instance; destination = cube.transform.position; } private void Update() { // Move our position a step closer to the target. float step = speed * Time.deltaTime; // calculate distance to move cube.transform.position = Vector3.MoveTowards(cube.transform.position, destination, step); if (Vector3.Distance(cube.transform.position, destination) < delta && Time.time > awaitingResponseUntilTimestamp) { Debug.Log("Destination reached."); PosRot cubePos = new PosRot( cube.transform.position.x, cube.transform.position.y, cube.transform.position.z, cube.transform.rotation.x, cube.transform.rotation.y, cube.transform.rotation.z, cube.transform.rotation.w ); PositionServiceRequest positionServiceRequest = new PositionServiceRequest(cubePos); // Send message to ROS and return the response ros.SendServiceMessage(serviceName, positionServiceRequest, Callback_Destination); awaitingResponseUntilTimestamp = Time.time+1.0f; // don't send again for 1 second, or until we receive a response } } void Callback_Destination(PositionServiceResponse response) { awaitingResponseUntilTimestamp = -1; destination = new Vector3(response.output.pos_x, response.output.pos_y, response.output.pos_z); Debug.Log("New Destination: " + destination); } } ``` - From the main menu bar, open `Robotics/ROS Settings`, and change the `ROS IP Address` variable to the ROS IP. - Create an empty GameObject and name it `RosService`. - Attach the `RosServiceExample` script to the `RosService` GameObject. Drag the cube GameObject onto its `cube` parameter. - Pressing play in the Editor should start communication with the `position_service` script, running as a ROS node, causing the cube to move to random positions in the scene. ![](images/tcp_3.gif)