ROS知识(5)----消息与服务的示例
ROS中已经定义了较多的标准类型的消息,你可以用在这些标准类型的消息上再自定义自己的消息类型。这个在复杂数据传输很有用,例如节点和服务器进行交互时,就可能用到传输多个参数到服务器,并返回相应的结果。为了保证例子的完整,将详述每一步。
基本思路和创建talker和listener的例子类似,步骤如下:
- 建立工作空间workspace(类似于vs下的解决方案,用来管理很多的项目);
- 建立包package(类似于vs下的项目);
- 创建msg和srv文件;
- 编写服务节点和客户节点代码;
- 利用rosmake进行编译(catkin_make也可以,但稍有不同,请参考另一篇博文的ROS知识(3));
- 利用rosrun运行;
1.1、创建工作空间
在开始具体工作之前,首先创建工作空间,并且为工作空间设置环境变量到~/.bashrc中,如果要查看已有的空间路径,可以用查询命令
$ echo $ROS_PACKAGE_PATH
你将会看到如下的信息:
/home/horsetail/dev/rosbook:/home/horsetail/catkin_ws/src:/opt/ros/jade/share:/opt/ros/jade/stacks
这里的创建空间实际上就是先建立一个文件夹,然后把文件夹的路径设置到环境变量~/.bashrc中。例如我们这里创建目录~/dev/rosbook作为工作空间。
首先执行命令:
$ cd ~
$ mkdir -p dev/rosbook
然后将创建的路径加入到环境变量中,执行如下命令:
$ echo "export ROS_PACKAGE_PATH=~/dev/rosbook:${ROS_PACKAGE_PATH}" >> ~/.bashrc
$ . ~/.bashrc
这样,我们就完成了工作空间的配置,注意:ROS安装的时候,一定要把ROS的环境变量也加到~/.bashrc中。这里还需要把ROS。接下来就是在这个空间下创建包了。
1.2、创建包
可以手动创建包,但是非常的繁琐,为了方便,最好使用roscreate-pkg命令行工具,该命令行的格式如下:
roscreate-pkg [package_name] [depend1] [depend2] [depend3] ...
命令行包含了要创建包的名字,依赖包。
我们的例子中,创建一个叫mypacakge1的 新包,命令如下:
$ cd ~/dev/rosbook
$ roscreate-pkg mypackage1 std_msgs roscpp rospy
过一会弹出如下的信息,表示创建成功:
Created package directory /home/horsetail/dev/rosbook/mypackage1
Created include directory /home/horsetail/dev/rosbook/mypackage1/include/mypackage1
Created cpp source directory /home/horsetail/dev/rosbook/mypackage1/src
Created package file /home/horsetail/dev/rosbook/mypackage1/Makefile
Created package file /home/horsetail/dev/rosbook/mypackage1/manifest.xml
Created package file /home/horsetail/dev/rosbook/mypackage1/CMakeLists.txt
Created package file /home/horsetail/dev/rosbook/mypackage1/mainpage.dox
Please edit mypackage1/manifest.xml and mainpage.dox to finish creating your package
好了这样就完成了包的创建,我们发现在mypackage1的目录下有一个src文件夹,我们接下来就是网这里添加源程序了。
1.3、创建msg和srv文件
首先,在mypackage1功能包下,创建msg文件夹,并在其中创建一个新的文件mypackage_msg1.msg,将在这个文件里自定义消息的类型,在文件中添加以下代码:
int32 A
int32 B
int32 C
现在编辑CMakeList.txt,从#rosbuild_genmsg()这一行中删除#,然后使用rosmake命令编译功能包:
$ rosmake mypackage1
为了检查正确性,使用rosmsg命令:
$ rosmsg show mypackage1/mypackage1_msg1
如果看到的内容和文件一样,说明编译正确。
现在新建一个srv文件,在mypackage1文件夹下建立srv文件夹,并在srv文件夹下新建一个文件mypackage1_srv1.srv,并添加以下代码:
int32 A int32 B int32 C --- int32 sum
编辑CMakeList.txt,从#rosbuild_genmsg()这一行中删除#,然后使用rosmake命令编译功能包,可以通过一下命令验证正确性:
$ rossrv show mypackage1/mypackage1_srv1
如果看到的内容和文件一样,说明编译正确。
1.4、编写服务节点和客户节点代码
接下来建立用于验证服务中请求响应的代码,在mypackage1/src下新建文件example_srv_request.cpp,添加如下代码:
#include "ros/ros.h" #include "mypackage1/mypackage_srv1.h" bool add(chapter2_tutorials::chapter2_srv1::Request &req, chapter2_tutorials::chapter2_srv1::Response &res) { res.sum = req.A + req.B + req.C; ROS_INFO("request: A=%ld, B=%ld C=%ld", (int)req.A, (int)req.B, (int)req.C); ROS_INFO("sending back response: [%ld]", (int)res.sum); return true; } int main(int argc, char **argv) { ros::init(argc, argv, "add_3_ints_server"); ros::NodeHandle n; ros::ServiceServer service = n.advertiseService("add_3_ints", add); ROS_INFO("Ready to add 3 ints."); ros::spin(); return 0; }
在mypackage1/src下新建文件example_srv_respone.cpp,添加如下代码:
#include "ros/ros.h" #include "mypackage1/mypackage_srv1.h" #include <cstdlib> int main(int argc, char **argv) { ros::init(argc, argv, "add_3_ints_client"); if (argc != 4) { ROS_INFO("usage: add_3_ints_client A B C "); return 1; } ros::NodeHandle n; ros::ServiceClient client = n.serviceClient<chapter2_tutorials::chapter2_srv1>("add_3_ints"); chapter2_tutorials::chapter2_srv1 srv; srv.request.A = atoll(argv[1]); srv.request.B = atoll(argv[2]); srv.request.C = atoll(argv[3]); if (client.call(srv)) { ROS_INFO("Sum: %ld", (long int)srv.response.sum); } else { ROS_ERROR("Failed to call service add_two_ints"); return 1; } return 0; }
接下来建立用于验证消息传递的代码,在mypackage1/src下新建文件example_talker_msg.cpp,添加如下代码:
#include "ros/ros.h" #include "mypackage1/mypackage1_msg1.h" #include <sstream> int main(int argc, char **argv) { ros::init(argc, argv, "example_talker_msg"); ros::NodeHandle n; ros::Publisher pub = n.advertise<chapter2_tutorials::chapter2_msg1>("message", 1000); ros::Rate loop_rate(10); while (ros::ok()) { chapter2_tutorials::chapter2_msg1 msg; msg.A = 1; msg.B = 2; msg.C = 3; pub.publish(msg); ros::spinOnce(); loop_rate.sleep(); } return 0; }
在mypackage1/src下新建文件example_listener_msg.cpp,添加如下代码:
#include "ros/ros.h" #include "mypackage1/mypackage1_msg1.h" void messageCallback(const chapter2_tutorials::chapter2_msg1::ConstPtr& msg) { ROS_INFO("I heard: [%d] [%d] [%d]", msg->A, msg->B, msg->C); } int main(int argc, char **argv) { ros::init(argc, argv, "example_listener_msg"); ros::NodeHandle n; ros::Subscriber sub = n.subscribe("message", 1000, messageCallback); ros::spin(); return 0; }
好了,至此完成了服务和消息的测试代码编写。
1.5、利用rosmake进行编译
接下来,要告诉编译器如何去找到这两个文件。你需要打开mypackage1/CMakeLists.txt,在文件的末尾添加两行命令:
rosbuild_add_executable(example_srv_request src/example_srv_request.cpp) rosbuild_add_executable(example_srv_respone src/example_srv_respone.cpp) rosbuild_add_executable(example_talker_msg src/example_talker_msg.cpp) rosbuild_add_executable(example_listener_msg src/example_listener_msg.cpp)
添加后的文件结构是这样的:
cmake_minimum_required(VERSION 2.4.6) include($ENV{ROS_ROOT}/core/rosbuild/rosbuild.cmake) # Set the build type. Options are: # Coverage : w/ debug symbols, w/o optimization, w/ code-coverage # Debug : w/ debug symbols, w/o optimization # Release : w/o debug symbols, w/ optimization # RelWithDebInfo : w/ debug symbols, w/ optimization # MinSizeRel : w/o debug symbols, w/ optimization, stripped binaries #set(ROS_BUILD_TYPE RelWithDebInfo) rosbuild_init() #set the default path for built executables to the "bin" directory set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin) #set the default path for built libraries to the "lib" directory set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib) #uncomment if you have defined messages rosbuild_genmsg() #uncomment if you have defined services rosbuild_gensrv() #common commands for building c++ executables and libraries
rosbuild_add_executable(example_srv_request src/example_srv_request.cpp)
rosbuild_add_executable(example_srv_respone src/example_srv_respone.cpp)
rosbuild_add_executable(example_talker_msg src/example_talker_msg.cpp)
rosbuild_add_executable(example_listener_msg src/example_listener_msg.cpp)
这样用rosmake命令来编译这个mypackage1包了。执行下面的命令:
$ rosmake mypackage1
输出下面的信息:
horsetail@horsetail-book:~$ roscore
... logging to /home/horsetail/.ros/log/6eae5b9c-628d-11e5-8bd7-3859f9722953/roslaunch-horsetail-book-6447.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.
started roslaunch server http://horsetail-book:44362/
ros_comm version 1.11.13
SUMMARY
========
PARAMETERS
* /rosdistro: jade
* /rosversion: 1.11.13
NODES
auto-starting new master
process[master]: started with pid [6459]
ROS_MASTER_URI=http://horsetail-book:11311/
...(内容太长了,省去)
[ rosmake ] Results:
[ rosmake ] Built 26 packages with 0 failures.
[ rosmake ] Summary output to directory
[ rosmake ] /home/horsetail/.ros/rosmake/rosmake_output-20150924-164014
哇,编译通过,大家注意到实际上也是用catkin进行编译的,额。我们来运行一下吧。
1.4、运行
首先打开一个新的终端,启动初始化ROS,执行命令:
$ roscore
先验证一下服务请求和相应的功能,需要在不同窗口分别执行以下命令:
rosrun mypackage1 example_talker_msg
rosrun mypackage1 example_listener_msg
可以看到请求listener的窗口,显示如下信息:
[ INFO] [1443154332.742277621]: I heard:[1][2][3] [ INFO] [1443164722.557755739]: I heard:[1][2][3] [ INFO] [1443164744.557858055]: I heard:[1][2][3]
好了至此完成了服务srv和消息msg的验证。
1.5、源码
最后,附上源码:mypackage1.tar.gz(这个是ROS机器人程序设计中第二章的例子,里面包含了消息和服务等例子)
参考资料
[1]. Aaron Martinez Enrique Fern andez, ROS机器人程序设计[B], P14-42, 2014.
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