如何实现一个ROS服务端呢

如何实现一个ROS服务端呢？有哪些实现步骤？

回帖（1）

王聪

2022-2-14 09:51:56

如何实现一个服务器
初始化ROS节点；
创建Server实例；
循环等待服务请求，进入回调函数；
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
#include
#include
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commandCallback
ros::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10
turtle_vel_pub = n.advertise("/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
1
#!/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/Trigger
import rospy
import thread,time
from geometry_msgs.msg import Twist
from std_srvs.srv import Trigger, TriggerResponse
pubCommand = 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 = 0.5
vel_msg.angular.z = 0.2
turtle_vel_pub.publish(vel_msg)
time.sleep(0.1)
def commandCallback(req):
global pubCommand
pubCommand = 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commandCallback
s = 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