service服务通信

服务通信

• 适用于对实时性有要求，有逻辑处理的应用场景
• 以请求响应的方式实现节点间通信

服务端——Server

客户端——Client

服务器端实现

1. 导入消息包中的srv

   1. c++/python 导包有所不同

2. 向NodeHandle申请初始化节点

3. 创建服务对象 server

4. 创建回调函数处理request，返回response

C++

#include <ros/ros.h>
#include <std_msgs/String.h>
#include <qq_msgs/AddInts.h>

bool donums(qq_msgs::AddInts::Request &request,
            qq_msgs::AddInts::Response &response){
    int num1 = request.num1;
    int num2 = request.num2;
    ROS_INFO("Get num1 = %d,num2 = %d", num1, num2);
    int sum = num1 + num2;
    response.sum = sum;
    ROS_INFO("Back sum = %d", sum);
    return true;
}


int main(int argc, char *argv[])
{
    setlocale(LC_ALL,"");

    ros::init(argc,argv,"test_server_node");

    ros::NodeHandle nh;
    
    ros::ServiceServer server = nh.advertiseService("AddInts",donums);

    ROS_INFO("Server Online");
    ros::spin();
}

Python

#!/usr/bin/env python3
#coding=utf-8

import rospy
from std_msgs.msg import String

#注意此处导包与 msg 有所不同 将下面的类型全部导入
from qq_msgs.srv import *	


def doNum(requset):
    num1 = requset.num1
    num2 = requset.num2

    sum = num1 + num2
    
    response = AddIntsResponse()

    response.sum = sum

    rospy.loginfo("Get num1:%d num2:%d",num1,num2)
    return response

if __name__ == "__main__":
    rospy.init_node("demo_server_node")

    server = rospy.Service("addInts", AddInts, doNum)
    rospy.loginfo("Server online")
    rospy.spin()

客户端实现

1. 向NodeHandle申请初始化节点
2. 创建客户端对象 client
3. 提交请求处理响应

C++

#include <ros/ros.h>
#include <std_msgs/String.h>
#include <qq_msgs/AddInts.h>


int main(int argc, char *argv[])
{
    setlocale(LC_ALL,"");

    ros::init(argc,argv,"test_client_node");

    ros::NodeHandle nh;
    
    ros::ServiceClient client = nh.serviceClient<qq_msgs::AddInts>("AddInts");

    //提交请求并处理响应

    qq_msgs::AddInts ai;
    ai.request.num1 = 10;
    ai.request.num2 = 100;

    bool flag = client.call(ai);    
    if(flag){
        int sum = ai.response.sum;
        ROS_INFO("Get sum = %d",sum);
    }
    else{
        ROS_INFO("Fail");
    }
    ros::spin();
}

客户端优化

实现参数动态提交

rosrun ros_pkg ros_node 12 34

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

    //优化实现，获取命令中参数
    setlocale(LC_ALL,"");

    if(argc != 3){
        ROS_INFO("参数个数不对");
        return 1;
    }

    ros::init(argc,argv,"test_client_node");

    ros::NodeHandle nh;
    
    ros::ServiceClient client = nh.serviceClient<qq_msgs::AddInts>("AddInts");

    //提交请求并处理响应

    qq_msgs::AddInts ai;
    ai.request.num1 = atoi(argv[1]);
    ai.request.num2 = atoi(argv[2]);

Python

#!/usr/bin/env python3
#coding=utf-8

import rospy
from std_msgs.msg import String
from qq_msgs.srv import *

if __name__ == "__main__":
    rospy.init_node("demo_client_node")

    client = rospy.ServiceProxy("addInts",AddInts)

    response = client.call(1,2)

    rospy.loginfo("Get %d",response.sum)

客户端优化

#!/usr/bin/env python3
#coding=utf-8

import rospy
from std_msgs.msg import String
from qq_msgs.srv import *
#导入sys包
import sys


if __name__ == "__main__":
	#判断参数个数
    if len(sys.argv) != 3:
        rospy.loginfo("参数个数不对")
        sys.exit(1)
    
    rospy.init_node("demo_client_node")

    client = rospy.ServiceProxy("addInts",AddInts)
	#传入参数
    num1 = int(sys.argv[1])
    num2 = int(sys.argv[2])
    response = client.call(num1,num2)

    rospy.loginfo("Get %d",response.sum)

挂起客户端，等待服务端

二者皆可使用

C++

• client.waitForExistence();
• ros::service::waitForService(“AddInts”);

Python

• client.wait_for_service()
• rospy.wait_for_service("addInts")

操作指令

rosservice 命令	作用
rosservice list	显示服务列表
rosservice info	打印服务信息
rosservice type	打印服务类型
rosservice uri	打印服务ROSRPC uri
rosservice find	按服务类型查找服务
rosservice call	使用所提供的args调用服务
rosservice args	打印服务参数