ROS通讯之 service通讯 原理及c++和python示例代码

一张图看懂service通讯

Service通讯分为client端和server端。

• client端负责发送请求(Request)给server端。
• server端负责接收client端发送的请求数据。
• server端收到数据后，根据请求数据和当前的业务需求，产生数据，将数据(Response)返回给client端。

Service通讯的特点：

• 同步数据访问
• 具有响应反馈机制
• 一个server多个client
• 注重业务逻辑处理

Service通讯的关键点：

• service的地址名称
• client端访问server端的数据格式
• server端响应client端的数据格式

c++ 代码如下

service:

#include <ros/ros.h>
#include <roscpp_tutorials/TwoInts.h>

bool callback(roscpp_tutorials::TwoInts::Request &request, roscpp_tutorials::TwoInts::Response &response) {
    response.sum = request.a + request.b;
    return true;
}

int main(int argc, char *argv[]) {

    ros::init(argc, argv, "service_node");
    ros::NodeHandle nodeHandle;
    const ros::ServiceServer &server = nodeHandle.advertiseService("my_service", callback);
    ros::spin();

}

client

#include <ros/ros.h>
#include <iostream>
#include <roscpp_tutorials/TwoInts.h>
using namespace std;
int main(int argc, char *argv[]) {
    ros::init(argc,argv,"client_node");
    ros::NodeHandle nodeHandle;
    ros::ServiceClient client = nodeHandle.serviceClient<roscpp_tutorials::TwoInts>("my_service");
//   等待服务端上线
    client.waitForExistence();
    roscpp_tutorials::TwoInts twoInts;
    twoInts.request.b = 10;
    twoInts.request.a = 20;
    client.call(twoInts);
    cout << twoInts.response.sum << endl;

}

python

service:

#!/usr/bin/env python
#coding:utf-8
import rospy
from roscpp_tutorials.srv import TwoInts ,TwoIntsResponse
def callback(request):
    response = TwoIntsResponse()

    response.sum = request.a + request.b;
    return  response


if __name__ == '__main__':
    rospy.init_node("py_service_node")
    rospy.Service("py_service",TwoInts,callback)
    rospy.spin()

client:

#!/usr/bin/env python
#coding:utf-8

import rospy
from roscpp_tutorials.srv import TwoInts,TwoIntsRequest,TwoIntsResponse

if __name__ == '__main__':
    nodeName = "py_clientnode"
    rospy.init_node(nodeName)
    rospy.wait_for_service()
    proxy = rospy.ServiceProxy("py_service", TwoInts)

    request = TwoIntsRequest()
    request.a = 10
    request.b = 20
    response = proxy.call(request)
    print response.sum
    rospy.spin()