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ROS–Unity Integration: Server Endpoint

A walkthrough of the important components of a ROS TCP endpoint script using the robotics_demo package as a example.

The following is an example of a server endpoint Python script that:

Gets parameters from rosparam
Creates corresponding ROS Publisher, Subscriber, and Service objects to interact with topics and services running in in ROS network
Starts TCP Server process to handle incoming and outgoing connections

#!/usr/bin/env python

import rospy

from ros_tcp_endpoint import TcpServer, RosPublisher, RosSubscriber, RosService

from robotics_demo.msg import PosRot, UnityColor
from robotics_demo.srv import PositionService

def main():
    ros_node_name = rospy.get_param("/TCP_NODE_NAME", 'TCPServer')
    buffer_size = rospy.get_param("/TCP_BUFFER_SIZE", 1024)
    connections = rospy.get_param("/TCP_CONNECTIONS", 10)
    tcp_server = TcpServer(ros_node_name, buffer_size, connections)

    tcp_server.source_destination_dict = {
        'pos_srv': RosService('position_service', PositionService),
        'pos_rot': RosPublisher('pos_rot', PosRot, queue_size=10),
        'color': RosSubscriber('color', UnityColor, tcp_server)
    }

    rospy.init_node(ros_node_name, anonymous=True)
    tcp_server.start()
    rospy.spin()


if __name__ == "__main__":
    main()

Import Statements for Services and Messages

from ros_tcp_endpoint import TcpServer, RosPublisher, RosSubscriber, RosService

from robotics_demo.msg import PosRot, UnityColor
from robotics_demo.srv import PositionService

Instantiate the ROS Node

    rospy.init_node(ros_node_name, anonymous=True)

ROS Publisher

A ROS Publisher requires three components:

Topic name
ROS message class generated from running catkin_make command
Queue size

RosPublisher('pos_rot', PosRot, queue_size=10)

ROS Subscriber

A ROS Subscriber requires three components:

Topic name
ROS message class generated from running catkin_make command
The tcp server that will connect to Unity

RosSubscriber('color', UnityColor, tcp_server)

ROS Service

A ROS Service requires two components:

Service name
ROS Service class generated from running catkin_make command

RosService('position_service', PositionService)

Creating the Server

Requires:

The ROS node name

    tcp_server = TcpServer(ros_node_name)

Source Destination Dictionary

Create a dictionary keyed by topic or service with the corresponding ROS communication class as the value. The dictionary is used by the TCP server to direct messages to and from the ROS network.

    tcp_server.source_destination_dict = {
        'pos_srv': RosService('position_service', PositionService),
        'pos_rot': RosPublisher('pos_rot', PosRot, queue_size=10),
        'color': RosSubscriber('color', Color, tcp_server),
    }

Starting the Server

    tcp_server.start()
    rospy.spin()

The following parameters can be hardcoded, but for the sake of portability, we recommend setting the parameters using the rosparam set command, or a rosparam YAML file.

    ros_node_name = rospy.get_param("/TCP_NODE_NAME", 'TCPServer')
    buffer_size = rospy.get_param("/TCP_BUFFER_SIZE", 1024)
    connections = rospy.get_param("/TCP_CONNECTIONS", 10)

In addition, the TCPServer class uses the ROS parameters ROS_IP and ROS_TCP_PORT to determine what ip & port to listen on.

Note: Read more about the ROS Parameter Server here.

Launch File

An example launch file that will set the appropriate ROSPARAM values required for a parameterized TCP Endpoint script.

<launch>

    <env name="ROS_IP" value="192.168.1.116"/>
    <env name="ROS_HOSTNAME" value="$(env ROS_IP)"/>
    
    <param name="ROS_IP" type="str" value="$(env ROS_IP)" />
    <param name="ROS_TCP_PORT" type="int" value="10000" />
    <param name="TCP_NODE_NAME" type="str" value="TCPServer" />

	<group ns="position_service_and_endpoint">
	       <node pkg="robotics_demo" name="position_service" type="position_service.py"/>
	       <node pkg="robotics_demo" name="server_endpoint" type="server_endpoint.py"/>
	</group>
</launch>

4.2 KiB 原始文件 文件历史