平台：华硕 Thinker Edge R 瑞芯微 RK3399Pro
固件版本：Tinker_Edge_R-Debian-Stretch-V1.0.4-20200615

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记录自【古月居】古月·ROS入门21讲 | 一学就会的ROS机器人入门教程 —— 古月居GYH P14 14.服务端Server的编程实现

如何实现一个服务器

1. 初始化ROS节点；
2. 创建Server实例；
3. 循环等待服务请求，进入回调函数；
4. 在回调函数中完成服务功能的处理，并反馈应答数据。

C++

编写程序

nano ~/catkin_workspace/src/learning_service/src/turtle_command_server.cpp

/***********************************************************************
Copyright 2020 GuYueHome (www.guyuehome.com).
***********************************************************************//*** 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger*/#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Trigger.h>ros::Publisher turtle_vel_pub;
bool pubCommand = false;// service回调函数，输入参数req，输出参数res
bool commandCallback(std_srvs::Trigger::Request  &req,std_srvs::Trigger::Response &res)
{pubCommand = !pubCommand;// 显示请求数据ROS_INFO("Publish turtle velocity command [%s]", pubCommand==true?"Yes":"No");// 设置反馈数据res.success = true;res.message = "Change turtle command state!";return true;
}int main(int argc, char **argv)
{// ROS节点初始化ros::init(argc, argv, "turtle_command_server");// 创建节点句柄ros::NodeHandle n;// 创建一个名为/turtle_command的server，注册回调函数commandCallbackros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback);// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);// 循环等待回调函数ROS_INFO("Ready to receive turtle command.");// 设置循环的频率ros::Rate loop_rate(10);while(ros::ok()){// 查看一次回调函数队列ros::spinOnce();// 如果标志为true，则发布速度指令if(pubCommand){geometry_msgs::Twist vel_msg;vel_msg.linear.x = 0.5;vel_msg.angular.z = 0.2;turtle_vel_pub.publish(vel_msg);}//按照循环频率延时loop_rate.sleep();}return 0;
}

配置CMakeLists.txt

nano ~/catkin_workspace/src/learning_service/CMakeLists.txt

添加

add_executable(turtle_command_server src/turtle_command_server.cpp)
target_link_libraries(turtle_command_server ${catkin_LIBRARIES})

编译并运行

cd ~/catkin_workspace
catkin_make# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
roscore
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosrun turtlesim turtlesim_node 
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosrun learning_service turtle_command_server
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosservice call /turtle_command "{}"rqt_graph

python

创建并编写脚本

nano ~/catkin_workspace/src/learning_service/scripts/turtle_command_server.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-########################################################################
####          Copyright 2020 GuYueHome (www.guyuehome.com).          ###
######################################################################### 该例程将执行/turtle_command服务，服务数据类型std_srvs/Triggerimport rospy
import thread,time
from geometry_msgs.msg import Twist
from std_srvs.srv import Trigger, TriggerResponsepubCommand = False;
turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)def command_thread():	while True:if pubCommand:vel_msg = Twist()vel_msg.linear.x = 0.5vel_msg.angular.z = 0.2turtle_vel_pub.publish(vel_msg)time.sleep(0.1)def commandCallback(req):global pubCommandpubCommand = bool(1-pubCommand)# 显示请求数据rospy.loginfo("Publish turtle velocity command![%d]", pubCommand)# 反馈数据return TriggerResponse(1, "Change turtle command state!")def turtle_command_server():# ROS节点初始化rospy.init_node('turtle_command_server')# 创建一个名为/turtle_command的server，注册回调函数commandCallbacks = rospy.Service('/turtle_command', Trigger, commandCallback)# 循环等待回调函数print "Ready to receive turtle command."thread.start_new_thread(command_thread, ())rospy.spin()if __name__ == "__main__":turtle_command_server()

运行

sudo chmod +x ~/catkin_workspace/src/learning_service/scripts/turtle_command_server.py# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
roscore
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosrun turtlesim turtlesim_node 
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosrun learning_service turtle_command_server.py 
# 新建一个终端
source ~/catkin_workspace/devel/setup.bash
rosservice call /turtle_command "{}"rqt_graph