9、 Alternative implementation of client for service communication

1、 Background

In service communication , Sometimes we need to create a new client , At this time, we can get service topics through relevant commands , data type , Thus, a new client sends a request to the server .

2、 Implementation steps

1. Create Feature Pack , Add dependency ：roscpp rospy std_msgs turtlesim

2. Get service topics and information

rosservice list
/clear
/key/get_loggers
/key/set_logger_level
/kill
/reset
/rosout/get_loggers
/rosout/set_logger_level
/spawn
/turtle/get_loggers
/turtle/set_logger_level
/turtle1/set_pen
/turtle1/teleport_absolute
/turtle1/teleport_relative
[email protected]:/media/d102/EPAN/Desktop/code_study_ubuntu/rosdemo_05$ rosservice type /spawn 
turtlesim/Spawn
[email protected]:/media/d102/EPAN/Desktop/code_study_ubuntu/rosdemo_05$ rossrv info turtlesim/Spawn
float32 x
float32 y
float32 theta
string name
---
string name
   

3. Code implementation

1. C++

   /*  The goal is ： Make a little turtle   service ：/spawn  Message type ：turtlesim/Spawn  Get ready ： start-up turtlesim_node node  */
   
   #include"ros/ros.h"
   #include"turtlesim/Spawn.h"
   
   int main(int argc, char *argv[]){
         
       setlocale(LC_ALL,"");
       ros::init(argc,argv,"turtle_add");
       ros::NodeHandle nh;
       //spawn For service topics 
       ros::ServiceClient client = nh.serviceClient<turtlesim::Spawn>("/spawn");
       ros::service::waitForService("/spawn");
       // establish spawn object 
       turtlesim::Spawn spawn;
       spawn.request.x = 1.0;
       spawn.request.y = 1.1;
       spawn.request.theta = 2.2;
       // When the tortoise name is repeated, it will report an error 
       spawn.request.name = "turtle_add1";
       bool flag = client.call(spawn);
       if (flag){
         
           ROS_INFO(" Tortoise name :%s",spawn.response.name.c_str());
       }
       else{
         
           ROS_INFO(" Failure ！！！");
       }
       return 0;
   }
   

2. Python

   #! /usr/bin/env python
   from tkinter import EXCEPTION
   from rosdep2 import RosdepLookup
   import rospy
   from turtlesim.srv import Spawn,SpawnRequest,SpawnResponse
   
   if __name__ == "__main__":
       rospy.init_node("turtle_add_p")
       client = rospy.ServiceProxy("/spawn",Spawn)
       client.wait_for_service()
       req = SpawnRequest()
       req.x = 1.0
       req.y = 4.3
       req.theta = 3.4
       req.name = "turtle_p"
       try:
           response = client.call(req)# Return tortoise name 
           rospy.loginfo(" Tortoise name ：%s",response.name)
       except EXCEPTION as e:
           rospy.loginfo(" Failure ！！！！！")