• ROS 消息订阅 服务器客户端客户端 通信方式

    理解服务

    服务service和消息msg的区别在于：

    1.  每一个消息都和一个话题相关，发布者对消息是发送后不管

    2.  消息可以一对多，也可以多对多

     3. 消息是单向的，没有响应的概念

    4.  每一个service服务由一个节点发起，服务的响应也返回同一个节点

     5. service服务是一对一通信

     6. service服务是双向的，并且响应是同步的

     7. service 由请求和响应构成

    查看服务

     查看服务的信息 $rosservice info [服务名]

     查看活动服务列表

    $rosservice list                                  小海龟示例。

    服务的组织：

    服务由请求、响应两部分构成，请求和响应之间通过“---”隔开，

    通常以srv为后缀放置在srv目录下。

    一个服务文件的示例如下：

    1. int64 a
    2. int64 b
    3.  
    4. --- 
    5.  
    6. int64  sum

    服务的每行声明和消息类型一样由两部分：

    域、变量构成，域由独立域、复合域构成，支持的基本数据类型和消息相同。

    服务的实现

    在实现上，服务在底层由一个GlobalCallbackQueue和ServiceManager管理，

    服务的请求req、响应resp本质上也是序列化的消息。

       

    在底层，客户端和服务器通过

    ServiceClientLink的boost::signals2::connection的信号、槽连接机制实现回调。

    自定义服务步骤：

     步骤1：创建自定义服务.srv

    1. int64 a
    2. int64 b
    3. ---
    4. int64 sum

     步骤2：编写服务文件service

    1. #include "ros/ros.h"
    2. #include "example_4/Sum.h"
    3.  
    4. bool add(example_4::Sum::Request  &req,
    5.          example_4::Sum::Response &res)
    6. {
    7.   res.sum = req.a + req.b;    // a+b 完成响应
    8.   ROS_INFO("request: x=%ld, y=%ld", (long int)req.a, (long int)req.b);
    9.   ROS_INFO("sending back response: [%ld]", (long int)res.sum);
    10.   return true;
    11. }
    12.  
    13. int main(int argc, char **argv)
    14. {
    15.   ros::init(argc, argv, "service");
    16.   ros::NodeHandle nh;
    17.  
    18.   ros::ServiceServer service = nh.advertiseService("add_two_ints", add); // 名字 + 回调名字
    19.   ROS_INFO("Ready to add two ints.");
    20.   ros::spin();
    21.  
    22.   return 0;
    23. }

     步骤3：编写客户端文件 client

    1. #include "ros/ros.h"
    2. #include "example_4/Sum.h"
    3. #include 
    4.  
    5. int main(int argc, char **argv)
    6. {
    7.   int a = 0,b = 0;
    8.   ros::init(argc, argv, "client");       // 表明是客户端
    9.   /*
    10.   if (argc != 3)
    11.   {
    12.     ROS_INFO("usage: add_two_ints_client X Y");
    13.     return 1;
    14.   }
    15.  */
    16.   ros::NodeHandle nh;
    17.   ros::ServiceClient client = nh.serviceClient("add_two_ints");
    18.   example_4::Sum srv;
    19.   if(nh.getParam("/client/client_x",a)){
    20.     srv.request.a = a;
    21.   }
    22.   if(nh.getParam("/client/client_y",b)){
    23.     srv.request.b = b;
    24.   }
    25.   //srv.request.a = atoll(argv[1]);
    26.   //srv.request.b = atoll(argv[2]);
    27.   if (client.call(srv))             //   调用 call 就可以发起请求
    28.   {
    29.     ROS_INFO("Sum: %ld", (long int)srv.response.sum);
    30.   }
    31.   else
    32.   {
    33.     ROS_ERROR("Failed to call service add_two_ints");
    34.     return 1;
    35.   }
    36.  
    37.   return 0;
    38. }

     步骤4：创建启动launch文件

    2.     
    3.     "service" pkg="example_4" type="service"  respawn="true"/>
    4.     
    5.     "client" pkg="example_4" type="client" output="screen">
    6.         "client_x" type="int" value="1" />
    7.         "client_y" type="int" value="5" />
    8.     
    10.  
    11.  
    12. #两个节点一个1
    13. #两个节点一个5

     步骤5：package.xml、CMakeLists.txt配置

    1. cmake_minimum_required(VERSION 3.0.2)
    2. project(example_4)
    3.  
    4. ## Compile as C++11, supported in ROS Kinetic and newer
    5. # add_compile_options(-std=c++11)
    6.  
    7. ## Find catkin macros and libraries
    8. ## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
    9. ## is used, also find other catkin packages
    10. find_package(catkin REQUIRED COMPONENTS
    11.   roscpp
    12.   rospy
    13.   std_msgs
    14.   message_generation
    15. )
    16.  
    17. ## System dependencies are found with CMake's conventions
    18. # find_package(Boost REQUIRED COMPONENTS system)
    19.  
    20.  
    21. ## Uncomment this if the package has a setup.py. This macro ensures
    22. ## modules and global scripts declared therein get installed
    23. ## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
    24. # catkin_python_setup()
    25.  
    26. ################################################
    27. ## Declare ROS messages, services and actions ##
    28. ################################################
    29.  
    30. ## To declare and build messages, services or actions from within this
    31. ## package, follow these steps:
    32. ## * Let MSG_DEP_SET be the set of packages whose message types you use in
    33. ##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).
    34. ## * In the file package.xml:
    35. ##   * add a build_depend tag for "message_generation"
    36. ##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET
    37. ##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in
    38. ##     but can be declared for certainty nonetheless:
    39. ##     * add a exec_depend tag for "message_runtime"
    40. ## * In this file (CMakeLists.txt):
    41. ##   * add "message_generation" and every package in MSG_DEP_SET to
    42. ##     find_package(catkin REQUIRED COMPONENTS ...)
    43. ##   * add "message_runtime" and every package in MSG_DEP_SET to
    44. ##     catkin_package(CATKIN_DEPENDS ...)
    45. ##   * uncomment the add_*_files sections below as needed
    46. ##     and list every .msg/.srv/.action file to be processed
    47. ##   * uncomment the generate_messages entry below
    48. ##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)
    49.  
    50. ## Generate messages in the 'msg' folder
    51. # add_message_files(
    52. #   FILES
    53. #   Message1.msg
    54. #   Message2.msg
    55. # )
    56.  
    57. ## Generate services in the 'srv' folder
    58.  add_service_files(
    59.    FILES
    60.    Sum.srv
    61.  )
    62.  
    63. ## Generate actions in the 'action' folder
    64. # add_action_files(
    65. #   FILES
    66. #   Action1.action
    67. #   Action2.action
    68. # )
    69.  
    70. ## Generate added messages and services with any dependencies listed here
    71.  generate_messages(
    72.    DEPENDENCIES
    73.    std_msgs
    74. )
    75.  
    76. ################################################
    77. ## Declare ROS dynamic reconfigure parameters ##
    78. ################################################
    79.  
    80. ## To declare and build dynamic reconfigure parameters within this
    81. ## package, follow these steps:
    82. ## * In the file package.xml:
    83. ##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"
    84. ## * In this file (CMakeLists.txt):
    85. ##   * add "dynamic_reconfigure" to
    86. ##     find_package(catkin REQUIRED COMPONENTS ...)
    87. ##   * uncomment the "generate_dynamic_reconfigure_options" section below
    88. ##     and list every .cfg file to be processed
    89.  
    90. ## Generate dynamic reconfigure parameters in the 'cfg' folder
    91. # generate_dynamic_reconfigure_options(
    92. #   cfg/DynReconf1.cfg
    93. #   cfg/DynReconf2.cfg
    94. # )
    95.  
    96. ###################################
    97. ## catkin specific configuration ##
    98. ###################################
    99. ## The catkin_package macro generates cmake config files for your package
    100. ## Declare things to be passed to dependent projects
    101. ## INCLUDE_DIRS: uncomment this if your package contains header files
    102. ## LIBRARIES: libraries you create in this project that dependent projects also need
    103. ## CATKIN_DEPENDS: catkin_packages dependent projects also need
    104. ## DEPENDS: system dependencies of this project that dependent projects also need
    105. catkin_package(
    106. #  INCLUDE_DIRS include
    107. #  LIBRARIES example_4
    108. #  CATKIN_DEPENDS roscpp rospy std_msgs
    109. #  DEPENDS system_lib
    110. )
    111.  
    112. ###########
    113. ## Build ##
    114. ###########
    115.  
    116. ## Specify additional locations of header files
    117. ## Your package locations should be listed before other locations
    118. include_directories(
    119. # include
    120.   ${catkin_INCLUDE_DIRS}
    121. )
    122.  
    123. ## Declare a C++ library
    124. # add_library(${PROJECT_NAME}
    125. #   src/${PROJECT_NAME}/example_4.cpp
    126. # )
    127.  
    128. ## Add cmake target dependencies of the library
    129. ## as an example, code may need to be generated before libraries
    130. ## either from message generation or dynamic reconfigure
    131. # add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
    132.  
    133. ## Declare a C++ executable
    134. ## With catkin_make all packages are built within a single CMake context
    135. ## The recommended prefix ensures that target names across packages don't collide
    136.  
    137. ## Rename C++ executable without prefix
    138. ## The above recommended prefix causes long target names, the following renames the
    139. ## target back to the shorter version for ease of user use
    140. ## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"
    141. # set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")
    142.  
    143. ## Add cmake target dependencies of the executable
    144. ## same as for the library above
    145. # add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
    146.  
    147. ## Specify libraries to link a library or executable target against
    148. if(CMAKE_BUILD_TYPE STREQUAL DEBUG)
    149. add_executable(service src/service.cpp)
    150. add_executable(client src/client.cpp)
    151. target_link_libraries(service
    152.    ${catkin_LIBRARIES}
    153. )
    154. target_link_libraries(client
    155.   ${catkin_LIBRARIES}
    156. )
    157. endif()
    158. #############
    159. ## Install ##
    160. #############
    161.  
    162. # all install targets should use catkin DESTINATION variables
    163. # See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html
    164.  
    165. ## Mark executable scripts (Python etc.) for installation
    166. ## in contrast to setup.py, you can choose the destination
    167. # catkin_install_python(PROGRAMS
    168. #   scripts/my_python_script
    169. #   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
    170. # )
    171.  
    172. ## Mark executables for installation
    173. ## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html
    174. # install(TARGETS ${PROJECT_NAME}_node
    175. #   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
    176. # )
    177.  
    178. ## Mark libraries for installation
    179. ## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html
    180. # install(TARGETS ${PROJECT_NAME}
    181. #   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
    182. #   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
    183. #   RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}
    184. # )
    185.  
    186. ## Mark cpp header files for installation
    187. # install(DIRECTORY include/${PROJECT_NAME}/
    188. #   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}
    189. #   FILES_MATCHING PATTERN "*.h"
    190. #   PATTERN ".svn" EXCLUDE
    191. # )
    192.  
    193. ## Mark other files for installation (e.g. launch and bag files, etc.)
    194. # install(FILES
    195. #   # myfile1
    196. #   # myfile2
    197. #   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
    198. # )
    199.  
    200. #############
    201. ## Testing ##
    202. #############
    203.  
    204. ## Add gtest based cpp test target and link libraries
    205. # catkin_add_gtest(${PROJECT_NAME}-test test/test_example_4.cpp)
    206. # if(TARGET ${PROJECT_NAME}-test)
    207. #   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
    208. # endif()
    209.  
    210. ## Add folders to be run by python nosetests
    211. # catkin_add_nosetests(test)

    package.xml

    1. "1.0"?>
    2. "2">
    3.   example_4
    4.   0.0.0
    5.   The example_4 package
    6.  
    7.   
    8.   
    9.   
    10.   "miaozl@todo.todo">miaozl
    11.  
    12.  
    13.   
    14.   
    15.   
    16.   D
    17.   O
    18.   O
    19.   T
    20.  
    21.  
    22.   
    23.   
    24.   
    25.   
    26.  
    27.  
    28.   
    29.   
    30.   
    31.   
    32.  
    33.  
    34.   
    35.   
    36.   
    37.   
    38.   
    39.   
    40.   
    41.   
    42.   
    43.   
    44.   
    45.   
    46.   
    47.   
    48.   
    49.   
    50.   
    51.   
    52.   
    53.   
    54.   catkin
    55.   roscpp
    56.   rospy
    57.   std_msgs
    58.   message_generation
    59.   roscpp
    60.   rospy
    61.   std_msgs
    62.   roscpp
    63.   rospy
    64.   std_msgs
    65.   message_runtime
    66.  
    67.  
    68.   
    69.   
    70.     
    71.  
    72.

     步骤6：生成服务文件  编译执行

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  • 原文地址：https://blog.csdn.net/weixin_44025389/article/details/126470105