【ROS教程】话题通信
@目录
[*]1.流程
[*]2.自定义发布数据
[*]2.1 std_msgs内置类型
[*]2.2 编写.msg文件
[*]2.3 修改package.xml文件
[*]2.3.1 完整的package.xml文件
[*]2.4 修改CMakeLists.txt文件
[*]2.4.1 修改find_package指令
[*]2.4.2 添加add_message_files指令
[*]2.4.3 添加generate_messages指令
[*]2.4.4 修改catkin_package指令
[*]2.5 查看头文件
[*]3.编写cpp文件
[*]3.1 功能包目录文件树
[*]3.2 修改CMakeLists.txt文件
[*]3.2.1 添加add_executable指令
[*]3.2.2 添加add_dependencies指令
[*]3.2.3 添加target_link_libraries指令
[*]3.2.4 完整的CMakeLists.txt
[*]3.3 发布方cpp
[*]3.4 订阅方cpp
[*]4.效果
1.流程
话题通信是ROS中使用频率最高的一种通信模式，话题通信是基于发布订阅模式的，也即:一个节点发布消息，另一个节点订阅该消息。在ROS中，实现话题通信只需要如下几步：
[*]确定要发布的数据类型，一般都需要自定义.msg文件，修改好CMakeLists.txt文件和package.xml文件并重编译
[*]编写发布方和订阅方的cpp文件，修改好CMakeLists.txt文件并重编译
[*]分别启动发布方节点和订阅方节点，顺序无所谓
2.自定义发布数据
在 ROS 通信协议中，数据载体是一个较为重要组成部分，ROS 中通过 std_msgs 封装了一些原生的数据类型。但是，这些数据一般只包含一个 data 字段，结构的单一意味着功能上的局限性，当传输一些复杂的数据， std_msgs 由于描述性较差而显得力不从心，这种场景下必须通过编写.msg文件来自定义消息类型。
2.1 std_msgs内置类型
[*]内置类型与 C++ 和 Python 中的对应关系:
Primitive TypeC++Pythonbooluint8_tboolint8int8_tintuint8uint8_tintint16int16_tintuint16uint16_tintint32uint32_tintuint64uint64_tlong intfloat32floatfloatfloat64doublefloatstringstd::stringstr bytestimeros::Timerospy.Timedurationros::Durationrospy.Duration
[*]内置类型的数组与 C++ 和 Python 中的对应关系:
Primitive TypeC++Pythonvariable-lengthstd::vectortuplefixed-lengthboost::array或std::vectortuple2.2 编写.msg文件
示例如下：
#文件名Person.msg
string name
uint16 age
float64 height2.3 修改package.xml文件
[*]查看是否存在如下编译依赖
<build_depend><exec_depend>message_generation</exec_depend></build_depend>
[*]查看是否存在如下执行依赖
<build_depend><exec_depend>message_generation</exec_depend></build_depend>2.3.1 完整的package.xml文件
chat0.0.0The chat package xu736946693 TODO catkin<build_depend><exec_depend>message_generation</exec_depend></build_depend>roscpprospystd_msgsroscpprospystd_msgs<build_depend><exec_depend>message_generation</exec_depend></build_depend>roscpprospystd_msgs 2.4 修改CMakeLists.txt文件
2.4.1 修改find_package指令
# 需要加入 <build_depend><exec_depend>message_generation</exec_depend></build_depend>,必须有 std_msgsfind_package(catkin REQUIRED COMPONENTSroscpprospystd_msgs<build_depend><exec_depend>message_generation</exec_depend></build_depend>)2.4.2 添加add_message_files指令
## 配置 msg 源文件
add_message_files(
FILES
Person.msg
)2.4.3 添加generate_messages指令
generate_messages(
DEPENDENCIES
std_msgs
)2.4.4 修改catkin_package指令
#执行时依赖
catkin_package(
#INCLUDE_DIRS include
#LIBRARIES demo02_talker_listener
CATKIN_DEPENDS roscpp rospy std_msgs message_runtime
#DEPENDS system_lib
)其中，add_message_files指令必须要在generate_messages指令的前面，然后在工作空间目录编译即可。
2.5 查看头文件
经过以上几步，在${workspace}/devel/include/${package}/目录下应该会出现一个头文件，如图：
[*]如果没有出现，是无法进行接下来的步骤的。这时，只需要把${workspace}/目录下的build目录和devel目录全部删除，然后重新编译即可。
rm -rf build/
rm -rf devel/
catkin_make3.编写cpp文件
3.1 功能包目录文件树
3.2 修改CMakeLists.txt文件
3.2.1 添加add_executable指令
add_executable(publisher
src/publisher.cpp)
add_executable(listener
src/listener.cpp)3.2.2 添加add_dependencies指令
add_dependencies(publisher ${PROJECT_NAME}_generate_messages_cpp)
add_dependencies(listener ${PROJECT_NAME}_generate_messages_cpp)3.2.3 添加target_link_libraries指令
target_link_libraries(person_talker
${catkin_LIBRARIES}
)
target_link_libraries(person_listener
${catkin_LIBRARIES}
)3.2.4 完整的CMakeLists.txt
[*]其中很多语句都是catkin_make自动生成的
cmake_minimum_required(VERSION 3.0.2)project(chat)## Compile as C++11, supported in ROS Kinetic and newer# add_compile_options(-std=c++11)## Find catkin macros and libraries## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)## is used, also find other catkin packagesfind_package(catkin REQUIRED COMPONENTSroscpprospystd_msgs<build_depend><exec_depend>message_generation</exec_depend></build_depend>)## System dependencies are found with CMake's conventions# find_package(Boost REQUIRED COMPONENTS system)## Uncomment this if the package has a setup.py. This macro ensures## modules and global scripts declared therein get installed## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html# catkin_python_setup()################################################## Declare ROS messages, services and actions #################################################### To declare and build messages, services or actions from within this## package, follow these steps:## * Let MSG_DEP_SET be the set of packages whose message types you use in## your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).## * In the file package.xml:## * add a build_depend tag for "<build_depend><exec_depend>message_generation</exec_depend></build_depend>"## * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET## * If MSG_DEP_SET isn't empty the following dependency has been pulled in## but can be declared for certainty nonetheless:## * add a exec_depend tag for "message_runtime"## * In this file (CMakeLists.txt):## * add "<build_depend><exec_depend>message_generation</exec_depend></build_depend>" and every package in MSG_DEP_SET to## find_package(catkin REQUIRED COMPONENTS ...)## * add "message_runtime" and every package in MSG_DEP_SET to## catkin_package(CATKIN_DEPENDS ...)## * uncomment the add_*_files sections below as needed## and list every .msg/.srv/.action file to be processed## * uncomment the generate_messages entry below## * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)# Generate messages in the 'msg' folder add_message_files( FILES Person.msg )## Generate services in the 'srv' folder# add_service_files(# FILES# Service1.srv# Service2.srv# )## Generate actions in the 'action' folder# add_action_files(# FILES# Action1.action# Action2.action# )## Generate added messages and services with any dependencies listed here# 生成消息时依赖于 std_msgsgenerate_messages( DEPENDENCIES std_msgs)################################################## Declare ROS dynamic reconfigure parameters #################################################### To declare and build dynamic reconfigure parameters within this## package, follow these steps:## * In the file package.xml:## * add a build_depend and a exec_depend tag for "dynamic_reconfigure"## * In this file (CMakeLists.txt):## * add "dynamic_reconfigure" to## find_package(catkin REQUIRED COMPONENTS ...)## * uncomment the "generate_dynamic_reconfigure_options" section below## and list every .cfg file to be processed## Generate dynamic reconfigure parameters in the 'cfg' folder# generate_dynamic_reconfigure_options(# cfg/DynReconf1.cfg# cfg/DynReconf2.cfg# )##################################### catkin specific configuration ####################################### The catkin_package macro generates cmake config files for your package## Declare things to be passed to dependent projects## INCLUDE_DIRS: uncomment this if your package contains header files## LIBRARIES: libraries you create in this project that dependent projects also need## CATKIN_DEPENDS: catkin_packages dependent projects also need## DEPENDS: system dependencies of this project that dependent projects also need#执行时依赖catkin_package( #INCLUDE_DIRS include #LIBRARIES demo02_talker_listener CATKIN_DEPENDS roscpp rospy std_msgs message_runtime #DEPENDS system_lib)############# Build ############### Specify additional locations of header files## Your package locations should be listed before other locationsinclude_directories(# include${catkin_INCLUDE_DIRS})## Declare a C++ library# add_library(${PROJECT_NAME}# src/${PROJECT_NAME}/pkg1.cpp# )## Add cmake target dependencies of the library## as an example, code may need to be generated before libraries## either from message generation or dynamic reconfigure# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})## Declare a C++ executable## With catkin_make all packages are built within a single CMake context## The recommended prefix ensures that target names across packages don't collide# add_executable(${PROJECT_NAME}_node src/pkg1_node.cpp)add_executable(publisher
src/publisher.cpp)
add_executable(listener
src/listener.cpp)## Rename C++ executable without prefix## The above recommended prefix causes long target names, the following renames the## target back to the shorter version for ease of user use## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")## Add cmake target dependencies of the executable## same as for the library above# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})add_dependencies(publisher ${PROJECT_NAME}_generate_messages_cpp)
add_dependencies(listener ${PROJECT_NAME}_generate_messages_cpp)## Specify libraries to link a library or executable target against# target_link_libraries(${PROJECT_NAME}_node# ${catkin_LIBRARIES}# )############### Install ################ all install targets should use catkin DESTINATION variables# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html## Mark executable scripts (Python etc.) for installation## in contrast to setup.py, you can choose the destination# catkin_install_python(PROGRAMS# scripts/my_python_script# DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}# )## Mark executables for installation## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html# install(TARGETS ${PROJECT_NAME}_node# RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}# )## Mark libraries for installation## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html# install(TARGETS ${PROJECT_NAME}# ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}# LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}# RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}# )## Mark cpp header files for installation# install(DIRECTORY include/${PROJECT_NAME}/# DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}# FILES_MATCHING PATTERN "*.h"# PATTERN ".svn" EXCLUDE# )## Mark other files for installation (e.g. launch and bag files, etc.)# install(FILES# # myfile1# # myfile2# DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}# )############### Testing ################# Add gtest based cpp test target and link libraries# catkin_add_gtest(${PROJECT_NAME}-test test/test_pkg1.cpp)# if(TARGET ${PROJECT_NAME}-test)# target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})# endif()target_link_libraries(publisher ${catkin_LIBRARIES} )target_link_libraries(listener ${catkin_LIBRARIES} )## Add folders to be run by python nosetests# catkin_add_nosetests(test)3.3 发布方cpp
示例如下：
/*
需求: 实现基本的话题通信，一方发布数据，一方接收数据，
实现的关键点:
1.发送方
2.接收方
3.数据
PS: 二者需要设置相同的话题
消息发布方:
循环发布信息:HelloWorld 后缀数字编号
实现流程:
1.包含头文件
2.初始化 ROS 节点:命名(唯一)
3.实例化 ROS 句柄
4.实例化 发布者 对象
5.组织被发布的数据，并编写逻辑发布数据
*/
// 1.包含头文件
#include "ros/ros.h"
#include "chat/Person.h"
int main(int argc, char*argv[])
{
//设置编码
setlocale(LC_ALL,"");
//2.初始化 ROS 节点:命名(唯一)
// 参数1和参数2 后期为节点传值会使用
// 参数3 是节点名称，是一个标识符，需要保证运行后，在 ROS 网络拓扑中唯一
ros::init(argc,argv,"talker");
//3.实例化 ROS 句柄
ros::NodeHandle nh;//该类封装了 ROS 中的一些常用功能
//4.实例化 发布者 对象
//泛型: 发布的消息类型
//参数1: 要发布到的话题
//参数2: 队列中最大保存的消息数，超出此阀值时，先进的先销毁(时间早的先销毁)
ros::Publisher pub = nh.advertise<chat::Person>("chatter",10);
//5.组织被发布的数据，并编写逻辑发布数据
//数据(动态组织)
chat::Person p;
p.name = "sunwukong";
p.age = 2000;
p.height = 1.45;
//逻辑(一秒1次)
ros::Rate r(1);
//节点不死
while (ros::ok())
{
//发布消息
pub.publish(p);
//加入调试，打印发送的消息
ROS_INFO("我叫:%s,今年%d岁,高%.2f米", p.name.c_str(), p.age, p.height);p.age++;
//根据前面制定的发送贫频率自动休眠 休眠时间 = 1/频率；
r.sleep();
//暂无应用
ros::spinOnce();
}
return 0;
}3.4 订阅方cpp
示例如下：
/*
需求: 实现基本的话题通信，一方发布数据，一方接收数据，
实现的关键点:
1.发送方
2.接收方
3.数据
消息订阅方:
订阅话题并打印接收到的消息
实现流程:
1.包含头文件
2.初始化 ROS 节点:命名(唯一)
3.实例化 ROS 句柄
4.实例化 订阅者 对象
5.处理订阅的消息(回调函数)
6.设置循环调用回调函数
*/
// 1.包含头文件
#include "ros/ros.h"
#include "chat/Person.h"
void doMsg(const chat::Person::ConstPtr& person_p){
ROS_INFO("订阅的人信息:%s, %d, %.2f", person_p->name.c_str(), person_p->age, person_p->height);
}
int main(int argc, char*argv[])
{
//设置编码
setlocale(LC_ALL,"");
//2.初始化 ROS 节点:命名(唯一)
ros::init(argc,argv,"listener");
//3.实例化 ROS 句柄
ros::NodeHandle nh;
//4.实例化 订阅者 对象
ros::Subscriber sub = nh.subscribe<chat::Person>("chatter",10,doMsg);
//5.处理订阅的消息(回调函数)
// 6.设置循环调用回调函数
ros::spin();//循环读取接收的数据，并调用回调函数处理
return 0;
}4.效果
[*]如果找不到可执行文件，就把工作目录下的build文件夹和devel文件夹删了重新编译。
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