content
service communication custom srv
Introduction
Service communication is also an extremely common communication mode in ROS. Service communication is based on the request-response mode and is a response mechanism. That is: a node A sends a request to another node B, B receives the processing request and generates a response result back to A
For example the following scenario:
During the patrol process of the robot, the control system analyzes the sensor data and finds suspicious objects or people... At this time, photos need to be taken and saved.
In the above scenario, service communication is used.
- A node needs to send a photo request to the camera node, the camera node processes the request, and returns the processing result
Similar to the above applications, service communication is more suitable for application scenarios that require timeliness and have certain logical processing.
The server starts, the client sends the client data, the server calculates and returns the result
theoretical model
service communication custom srv
Create a new feature pack
build dependencies
create srv
Then create a custom srv
Copy the code below
int32 num1
int32 num2
---
int32 sumNote: --- used to separate request and response
Edit configuration file
Depends on this package when building
Build service
build dependencies
This is the dependent package in find_package
Then
ctrl shift b compile it
will generate a lot of intermediate files
Generate requester (client) files
Generate server files
request content
Service Content
Corresponding files are also generated in python
summary:
In fact, it is very similar to msg, except that there is one more --- to distinguish between request and response messages
C++ implementation
process
- write server-side implementation;
- write client implementation;
- edit configuration file;
- Compile and execute.
vscode configuration
copy path
Server implementation
Copy the code below
/*
需求:
编写两个节点实现服务通信，客户端节点需要提交两个整数到服务器
服务器需要解析客户端提交的数据，相加后，将结果响应回客户端，
客户端再解析
服务器实现:
1.包含头文件
2.初始化 ROS 节点
3.创建 ROS 句柄
4.创建 服务 对象
5.回调函数处理请求并产生响应
6.由于请求有多个，需要调用 ros::spin()
*/
#include "ros/ros.h"
#include "demo03_server_client/AddInts.h"
// bool 返回值由于标志是否处理成功
bool doReq(demo03_server_client::AddInts::Request& req,
demo03_server_client::AddInts::Response& resp){
int num1 = req.num1;
int num2 = req.num2;
ROS_INFO("服务器接收到的请求数据为:num1 = %d, num2 = %d",num1, num2);
//逻辑处理
if (num1 < 0 || num2 < 0)
{
ROS_ERROR("提交的数据异常:数据不可以为负数");
return false;
}
//如果没有异常，那么相加并将结果赋值给 resp
resp.sum = num1 + num2;
return true;
}
int main(int argc, char *argv[])
{
setlocale(LC_ALL,"");
// 2.初始化 ROS 节点
ros::init(argc,argv,"AddInts_Server");
// 3.创建 ROS 句柄
ros::NodeHandle nh;
// 4.创建 服务 对象
ros::ServiceServer server = nh.advertiseService("AddInts",doReq);
ROS_INFO("服务已经启动....");
// 5.回调函数处理请求并产生响应
// 6.由于请求有多个，需要调用 ros::spin()
ros::spin();
return 0;
}
CMakeLists configuration
ctrl / uncomment
Some errors above can be corrected by looking at the picture below
then test
Client implementation
/*
需求:
编写两个节点实现服务通信，客户端节点需要提交两个整数到服务器
服务器需要解析客户端提交的数据，相加后，将结果响应回客户端，
客户端再解析
服务器实现:
1.包含头文件
2.初始化 ROS 节点
3.创建 ROS 句柄
4.创建 客户端 对象
5.请求服务，接收响应
*/
// 1.包含头文件
#include "ros/ros.h"
#include "demo03_server_client/AddInts.h"
int main(int argc, char *argv[])
{
setlocale(LC_ALL,"");
// 调用时动态传值,如果通过 launch 的 args 传参，需要传递的参数个数 +3
if (argc != 3)
// if (argc != 5)//launch 传参(0-文件路径 1传入的参数 2传入的参数 3节点名称 4日志路径)
{
ROS_ERROR("请提交两个整数");
return 1;
}
// 2.初始化 ROS 节点
ros::init(argc,argv,"AddInts_Client");
// 3.创建 ROS 句柄
ros::NodeHandle nh;
// 4.创建 客户端 对象
ros::ServiceClient client = nh.serviceClient<demo03_server_client::AddInts>("AddInts");
//等待服务启动成功
//方式1
ros::service::waitForService("AddInts");
//方式2
// client.waitForExistence();
// 5.组织请求数据
demo03_server_client::AddInts ai;
ai.request.num1 = atoi(argv[1]);
ai.request.num2 = atoi(argv[2]);
// 6.发送请求,返回 bool 值，标记是否成功
bool flag = client.call(ai);
// 7.处理响应
if (flag)
{
ROS_INFO("请求正常处理,响应结果:%d",ai.response.sum);
}
else
{
ROS_ERROR("请求处理失败....");
return 1;
}
return 0;
}
Modify CMakeLists
Then
ctrl shift b compile
start testing
type in data
optimization
restart the server
That's it
Python implementation
Server implementation
Create a new file and copy the following code
#! /usr/bin/env python
"""
需求:
编写两个节点实现服务通信，客户端节点需要提交两个整数到服务器
服务器需要解析客户端提交的数据，相加后，将结果响应回客户端，
客户端再解析
服务器端实现:
1.导包
2.初始化 ROS 节点
3.创建服务对象
4.回调函数处理请求并产生响应
5.spin 函数
"""
# 1.导包
import rospy
from demo03_server_client.srv import AddInts,AddIntsRequest,AddIntsResponse
# 回调函数的参数是请求对象，返回值是响应对象
def doReq(req):
# 解析提交的数据
sum = req.num1 + req.num2#num1、num2来自于.srv文件
rospy.loginfo("提交的数据:num1 = %d, num2 = %d, sum = %d",req.num1, req.num2, sum)
# 创建响应对象，赋值并返回
# resp = AddIntsResponse()
# resp.sum = sum
resp = AddIntsResponse(sum)
return resp
if __name__ == "__main__":
# 2.初始化 ROS 节点
rospy.init_node("addints_server_p")
# 3.创建服务对象
server = rospy.Service("AddInts",AddInts,doReq)
# 4.回调函数处理请求并产生响应
# 5.spin 函数
rospy.spin()
grant execute permission
Configure CMakeLists
then compile
Client implementation
create a new file
Copy the code below
#! /usr/bin/env python
"""
需求:
编写两个节点实现服务通信，客户端节点需要提交两个整数到服务器
服务器需要解析客户端提交的数据，相加后，将结果响应回客户端，
客户端再解析
客户端实现:
1.导包
2.初始化 ROS 节点
3.创建请求对象
4.发送请求
5.接收并处理响应
优化:
加入数据的动态获取
"""
#1.导包
import rospy
from demo03_server_client.srv import *
import sys
if __name__ == "__main__":
#优化实现
if len(sys.argv) != 3:
rospy.logerr("请正确提交参数")
sys.exit(1)
# 2.初始化 ROS 节点
rospy.init_node("AddInts_Client_p")
# 3.创建请求对象
client = rospy.ServiceProxy("AddInts",AddInts)
# 请求前，等待服务已经就绪
# 方式1:
# rospy.wait_for_service("AddInts")
# 方式2
client.wait_for_service()
# 4.发送请求,接收并处理响应
# 方式1
# resp = client(3,4)
# 方式2
# resp = client(AddIntsRequest(1,5))
# 方式3
req = AddIntsRequest()
# req.num1 = 100
# req.num2 = 200
#优化
req.num1 = int(sys.argv[1])
req.num2 = int(sys.argv[2])
resp = client.call(req)
rospy.loginfo("响应结果:%d",resp.sum)
Granted permission
Modify CMakeLists
then compile
Do a terminal test
