摘要：
开始时，教程包如下所示。1.创建msg文件夹和srv文件夹。2.然后更改CMakeList。txt文件转换为以下内容，主要设计msg和srv的其他依赖关系以及编译和运行关系##Findcatkinmacrosandlibraries##ifCOMPONENTSlistlikefind_ package##，还可以找到其他catkinpackagesfind_package##在'msg'文件夹中生成消息messages_files##在'srv'文件夹中产生服务add_service_files##生成具有此处列出的任何依赖项的添加消息和服务generate_messages#include_directoriesinclude_directories_catkin_也可以引用包。在wiki中，CreatingMsgAndSrv中的进程名称没有更改，但文件中的内容已更改。重写后，您可以单击ws目录下的catkin_catkin一次，然后单击sourcedevel/setup.bash下的。
简介：介绍如何在一个node里调用现有的rosservice list查询到的service。
效果：通过talker publish需要调用服务的数据，listener接收到数据后调用服务进行三个整形数据相加，并返回相加和。
环境：ubuntu 14.04 +indigo.
备注：文中未详细介绍的api或ros的基本函数请参看之前博文。
[正文]
创建过程类似wiki教程中msg和srv的测试过程。在beginner_turtorials包下面创建。
1，创建msg文件夹，srv文件夹。
msg 文件夹下创建Num.msg，内容是
int32 A
int32 B
int32 C
srv文件夹下AddTwoInts.srv，内容是
int32 A
int32 B
int32 C
---
int32 sum
该文件表面输入是ABC，返回是 sum，两者通过“---”分割。
2，然后更改CMakeList.txt文件，修改为如下内容，主要设计msg，srv的其他依赖关系及编译运行的相关关系。
## Find catkin macros and libraries ## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz) ## is used, also find other catkin packages find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs message_generation )
## Generate messages in the 'msg' folder add_message_files( FILES Num.msg ) ## Generate services in the 'srv' folder add_service_files( FILES AddTwoInts.srv )
## Generate added messages and services with any dependencies listed here generate_messages( DEPENDENCIES std_msgs )
# include_directories(include)
include_directories(
${catkin_INCLUDE_DIRS}
)
catkin_package( # INCLUDE_DIRS include # LIBRARIES beginner_tutorials # CATKIN_DEPENDS roscpp rospy std_msgs # DEPENDS system_lib CATKIN_DEPENDS message_runtime )
也可参考，wiki中CreatingMsgAndSrv中过程，名称都没有改变，只是改变了文件中内容，改写完成后可以在catkin_ws目录下catkin_make一次，并source devel/setup.bash下。
3，建立几个cpp的源文件，位于src目录下。
3.1 src/example_srv_request.cpp
作用：主要实现服务的定义，初始化，注释由于ubuntu没装汉语输入，因此注释为英文...聊胜于无。
#include "ros/ros.h"
#include "beginner_tutorials/AddTwoInts.h"
bool add(beginner_tutorials::AddTwoInts::Request &req,
beginner_tutorials::AddTwoInts::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;
//init service:
//Name: add_3_ints,advertise the service. add: call back function
ros::ServiceServer service=n.advertiseService("add_3_ints",add);
ROS_INFO("Ready to add 3 ints.");
ros::spin();// start to deal with the call back event
return 0;
}3.2 src/example_srv_response.cpp，该文件并非必要，是典型的client调用服务的形式，并非此文目的，不添加最终目的也可实现，调用示例是(现在还不能调用)： rosrun beginner_tutorials example_srv_response 1 2 3
#include "ros/ros.h"
#include "beginner_tutorials/AddTwoInts.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<beginner_tutorials::AddTwoInts>("add_3_ints");
beginner_tutorials::AddTwoInts srv;
//atoll:convert a string to long long int variable
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_three_ints");
return 1;
}
return 0;
}
3.3 src/example_talker_msg.cpp 该文件主要实现3个参数的发布，此处发布了A=1,B=2,C=3；
#include "ros/ros.h"
#include "beginner_tutorials/Num.h"
#include <sstream>
//Usage:publish a msg with topic named message
int main(int argc, char **argv)
{
ros::init(argc, argv, "example_talker_msg");
ros::NodeHandle n;
//advertise a topic named "message"
ros::Publisher pub=n.advertise<beginner_tutorials::Num>("message",1000);
ros::Rate loop_rate(10);
while (ros::ok())
{
beginner_tutorials::Num msg;
msg.A=1;
msg.B=2;
msg.C=3;
pub.publish(msg);
ros::spinOnce();
loop_rate.sleep();
}
return 0;
}
3.4 src/example_listener_msg.cpp 该文件主要实现对前文talker发布的数据的监听，监听到Num类型定义数据后，通过service: ros::service::call / client.call()两种方式进行add_3_ints服务的调用。
#include "ros/ros.h"
#include "beginner_tutorials/Num.h"
#include "beginner_tutorials/AddTwoInts.h"
//declaration of the Example class:construct function, member and so on.
class Example{
public:
Example();
private:
ros::NodeHandle nh;
ros::ServiceClient client;
ros::Subscriber listener;
void messageCallback(const beginner_tutorials::Num::ConstPtr& msg);
};
//implementation of construct function.
Example::Example()
{
client=nh.serviceClient<beginner_tutorials::AddTwoInts>("add_3_ints");
//monitor a topic named "message",this -> current object,pointer
listener=nh.subscribe("message",1000,&Example::messageCallback,this);
}
//implementation of one of the Example class memeber.
void Example::messageCallback( const beginner_tutorials::Num::ConstPtr& msg)
{
// ROS_INFO("I heard:[%d] [%d] [%d]",msg->A,msg->B,msg->C);
beginner_tutorials::AddTwoInts srv;
srv.request.A=msg->A;
srv.request.B=msg->B;
srv.request.C=msg->C;
if(ros::service::call("add_3_ints",srv))
ROS_INFO("SUM: %ld",(long int)srv.response.sum);
else
ROS_ERROR("Failed to call service add_three_ints");
/*
if(client.call(srv))
{
ROS_INFO("SUM: %ld",(long int)srv.response.sum);
}
else
{
ROS_ERROR("Failed to call service add_three_ints");
}
*/
}
int main(int argc, char **argv)
{
ros::init(argc, argv, "example_listener_msg");
Example exp;
ros::spin();
return 0;
}
4 再次修改CMakeList.txt文件添加编译链接的相关控制语句。
add_executable(example_srv_request src/example_srv_request.cpp)
target_link_libraries(example_srv_request ${catkin_LIBRARIES})
add_executable(example_srv_response src/example_srv_response.cpp)
target_link_libraries(example_srv_response ${catkin_LIBRARIES})
add_executable(example_talker_msg src/example_talker_msg.cpp)
target_link_libraries(example_talker_msg ${catkin_LIBRARIES})
add_executable(example_listener_msg src/example_listener_msg.cpp)
target_link_libraries(example_listener_msg ${catkin_LIBRARIES})添加后在工作空间主目录cd ~/catkin_ws下进行catkin_make编译，理论上不会出现问题，若有问题检查自己包和msg，srv的生成及cmakelist文件。5 测试
一个终端运行命令：roscore,
一个终端运行命令（注意此时近乎所有命令和包的名称及可执行文件名称都可以<table>自动补全）：rosrun beginner_tutorials example_srv_request；会返回： [INFO][时间戳]：Ready to add 3 ints. 此时若通过roservice list查询ros提供的服务则会返回add_3_ints等几个服务。
一个终端运行命令：rosrun beginner_tutorials example_talker_msg
一个终端运行命令：rosrun beginner_tutorials example_listener_msg；此时会返回： [INFO][时间戳]：SUM: 6
在此文件中，我们实现了在一个node中以下面两种方式对add_3_ints的服务调用，而不是在命令行中通过rosrun beginner_tutorials example_srv_response 1 2 3调用。
if(ros::service::call("add_3_ints",srv))
ROS_INFO("SUM: %ld",(long int)srv.response.sum);
else
ROS_ERROR("Failed to call service add_three_ints");
/*
if(client.call(srv))
{
ROS_INFO("SUM: %ld",(long int)srv.response.sum);
}
else
{
ROS_ERROR("Failed to call service add_three_ints");
}
*/