创建代码

turtle_command_server.cpp

/*** 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;
}

修改cmake

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

编译

catkin_make

运行

roscore

rosrun turtlesim turtlesmi_node

rosrun service_example turtle_command_server

rosservice call /turtle_command tab键