1.编写发布者节点

在之前创建的study/src目录下创建talker.cpp文件并粘贴以下内容进去

#include "ros/ros.h"
#include "std_msgs/String.h"#include <sstream>/*** This tutorial demonstrates simple sending of messages over the ROS system.*/
int main(int argc, char **argv)
{/*** The ros::init() function needs to see argc and argv so that it can perform* any ROS arguments and name remapping that were provided at the command line.* For programmatic remappings you can use a different version of init() which takes* remappings directly, but for most command-line programs, passing argc and argv is* the easiest way to do it.  The third argument to init() is the name of the node.** You must call one of the versions of ros::init() before using any other* part of the ROS system.*/ros::init(argc, argv, "talker");/*** NodeHandle is the main access point to communications with the ROS system.* The first NodeHandle constructed will fully initialize this node, and the last* NodeHandle destructed will close down the node.*/ros::NodeHandle n;/*** The advertise() function is how you tell ROS that you want to* publish on a given topic name. This invokes a call to the ROS* master node, which keeps a registry of who is publishing and who* is subscribing. After this advertise() call is made, the master* node will notify anyone who is trying to subscribe to this topic name,* and they will in turn negotiate a peer-to-peer connection with this* node.  advertise() returns a Publisher object which allows you to* publish messages on that topic through a call to publish().  Once* all copies of the returned Publisher object are destroyed, the topic* will be automatically unadvertised.** The second parameter to advertise() is the size of the message queue* used for publishing messages.  If messages are published more quickly* than we can send them, the number here specifies how many messages to* buffer up before throwing some away.*/ros::Publisher chatter_pub = n.advertise<std_msgs::String>("chatter", 1000);ros::Rate loop_rate(10);/*** A count of how many messages we have sent. This is used to create* a unique string for each message.*/int count = 0;while (ros::ok()){/*** This is a message object. You stuff it with data, and then publish it.*/std_msgs::String msg;std::stringstream ss;ss << "hello world " << count;msg.data = ss.str();ROS_INFO("%s", msg.data.c_str());/*** The publish() function is how you send messages. The parameter* is the message object. The type of this object must agree with the type* given as a template parameter to the advertise<>() call, as was done* in the constructor above.*/chatter_pub.publish(msg);ros::spinOnce();loop_rate.sleep();++count;}return 0;
}

这部分代码的解读，可参考：添加链接描述

2. 编写订阅者节点

在src目录下创建listener.cpp文件并粘贴以下内容进去：

#include "ros/ros.h"
#include "std_msgs/String.h"/*** This tutorial demonstrates simple receipt of messages over the ROS system.*/
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{ROS_INFO("I heard: [%s]", msg->data.c_str());
}int main(int argc, char **argv)
{/*** The ros::init() function needs to see argc and argv so that it can perform* any ROS arguments and name remapping that were provided at the command line.* For programmatic remappings you can use a different version of init() which takes* remappings directly, but for most command-line programs, passing argc and argv is* the easiest way to do it.  The third argument to init() is the name of the node.** You must call one of the versions of ros::init() before using any other* part of the ROS system.*/ros::init(argc, argv, "listener");/*** NodeHandle is the main access point to communications with the ROS system.* The first NodeHandle constructed will fully initialize this node, and the last* NodeHandle destructed will close down the node.*/ros::NodeHandle n;/*** The subscribe() call is how you tell ROS that you want to receive messages* on a given topic.  This invokes a call to the ROS* master node, which keeps a registry of who is publishing and who* is subscribing.  Messages are passed to a callback function, here* called chatterCallback.  subscribe() returns a Subscriber object that you* must hold on to until you want to unsubscribe.  When all copies of the Subscriber* object go out of scope, this callback will automatically be unsubscribed from* this topic.** The second parameter to the subscribe() function is the size of the message* queue.  If messages are arriving faster than they are being processed, this* is the number of messages that will be buffered up before beginning to throw* away the oldest ones.*/ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);/*** ros::spin() will enter a loop, pumping callbacks.  With this version, all* callbacks will be called from within this thread (the main one).  ros::spin()* will exit when Ctrl-C is pressed, or the node is shutdown by the master.*/ros::spin();return 0;
}

3.构建节点

前面的介绍使用了catkin_create_pkg，它创建了一个和一个package.xml和CMakeLists.txt文件。只需将这几行添加到CMakeLists.txt文件的底部：

add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_dependencies(talker study_generate_messages_cpp)add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
add_dependencies(listener study_generate_messages_cpp)

这将创建两个可执行文件talker和listener，默认情况下，它们将被放到软件包目录下的devel空间中，即~/catkin_ws/devel/lib/。

现在可以运行catkin_make：

# 在你的catkin工作空间下
$ cd ~/catkin_ws
$ catkin_make

4.运行节点

打开一个终端，运行roscore；
再打开一个新的终端，运行接收节点：rosrun study listener
再打开一个新的终端，运行发布节点：rosrun study talker
再打开一个新的终端，运行rqt_graph，可以看到：

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编写简单的发布者和订阅者(C++)---ROS学习第9篇

文章目录

1.编写发布者节点

2. 编写订阅者节点

3.构建节点

4.运行节点

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