[ROS] handwritten message publisher and subscriber

This article records handwriting ROS The process of message publisher and subscriber ,(C++ edition )
development environment ：VSCode Ubuntu18.04

Pre development preparation

1 Import the library files required for development

Need to prepare for development ROS Package library

2 Open established ros Development folder , For the establishment process, see Workspace creation and Function package creation

And then I found out VSCode Automatically import the created folder , below src In the catalog test_tutorials For feature packs created in the workspace , stay /test_tutorials/src Under the new talker.cpp

Suppose the environment is ready , Next is the process of development .

Handwriting publisher

1 The code is as follows

#include "ros/ros.h"
#include "std_msgs/String.h"
#include <sstream>
// At a certain frequency (10hz) Release information to fixed topics (hello world + count)

int main(int argc,char **argv){
    
    // initialization ros The name of the node   only 
    ros::init(argc,argv,"talker");
    ros::NodeHandle n;
    // Declare publisher   With std_msgs::String Form orientation chatter  Topic name  1000 Cache for topics 
    ros::Publisher chatter_pub=n.advertise<std_msgs::String>("chatter",1000);
    //  The cycle frequency is 10hz
    ros::Rate loop_rate(10);

    int count=0;
    // ros::ok()  If the node is always on  true  otherwise   by  false
    while(ros::ok()){
    
        std_msgs::String msg;
        std::stringstream ss;
        ss<<"hello world "<<count;

        msg.data=ss.str(); //  Get message data 
        ROS_INFO("%s",msg.data.c_str());//  Print message data 
        chatter_pub.publish(msg);// Post topic news 
        ros::spinOnce();//ros  Callback function   General plus 
        loop_rate.sleep();// Call the frequency function   rest 10hz
        ++count; //  Counter increment 
    }
    return 0 ;
}

2 To write CmakeLists.txt Content

Pay attention to the open CmakeLists.txt Directory structure of

Then add the following

# Import and stock in documents 
include_directories(include ${catkin_INCLUDE_DIRS})
#  Generate execution file 
add_executable(talker src/talker.cpp)
#  The generated talker  File link to catkin_LIBRARIES
target_link_libraries(talker ${catkin_LIBRARIES})

3 compile

Open the terminal and switch to the workspace folder , Input

catkin_make

Compile

Compile successfully

4 Run to check whether the publisher is successful

Open a terminal start-up roscore

roscore

Open another terminal , Input

rosrun test_tutorials talker // test_tutorials  Name the function package ,talker For Publisher 

Open another terminal Look at the chart
Check if... Exists first chatter topic of conversation

rostopic list

Just open roscore

open roscore and talker node

Look at the chart

rosrun rqt_graph rqt_graph

It means that the handwriting publisher is successful .

Handwriting subscriber

1 Code

#include "ros/ros.h"
#include "std_msgs/String.h"
//#include <sstream>

// The callback function parameters are consistent with the publisher information type 
void chatterCallback(const std_msgs::String::ConstPtr& msg){
    
    // Print the information heard by the listener 
    ROS_INFO("I hear [%s]",msg->data.c_str());
}
int main(int argc,char **argv){
    
   // initialization ros node   The name is unique 
    ros::init(argc,argv,"listener");
    // Statement ros  Handle 
    ros::NodeHandle n;
    // Declare a subscriber  1000 Subscriber cache   And call the callback function 
    ros::Subscriber sub=n.subscribe("chatter",1000,chatterCallback);
    // Blocking callback   Be similar to 
    /* while(ros::ok()){ros::spinOnce();} */
    ros::spin(); 
    return 0;
}

2 To write CmakeLists.txt

# Import and stock in documents 
include_directories(include ${catkin_INCLUDE_DIRS})
#  Generate execution file 
add_executable(talker src/talker.cpp)
#  The generated talker  File link to catkin_LIBRARIES
target_link_libraries(talker ${catkin_LIBRARIES})

#  Generate execution file 
add_executable(listener src/listener.cpp)
#  The generated talker  File link to catkin_LIBRARIES
target_link_libraries(listener ${catkin_LIBRARIES})

3 compile catkin_make

4 And commissioning talker equally , open listener

rosrun test_tutorials listener

This is Publisher talker

listener

Calculation chart

The above is the process of writing simple message publishers and subscribers , I hope it will be of some help to you .