How to subscribe and publish to /points_map topic

asked 2020-01-22 01:25:49 -0500

crazyRan
5 ●5 ●6 ●9

updated 2020-01-22 19:59:31 -0500

Here's my code:

foreignTopic::foreignTopic() {
    chat_= n.advertise<sensor_msgs::PointCloud2>("multimaster/chatter", 1000);
}

void foreignTopic::callback(const sensor_msgs::PointCloud2::ConstPtr& msg){
    chat_.publish(msg);
}

void multimaster::init(ros::M_string remappings) {

    ros::Rate loop_rate(msgsFrequency_Hz);     
                 foreignTopic pc; 
    //Create subscribers in the host and connect them to the foreign topics 
    remappings["__master"] = host_master;
    ros::master::init(remappings);
    ros::Subscriber subscriberFeedback = nh.subscribe("/points_map", 1, &foreignTopic::callback, &pc);  
    remappings["__master"] =  foreign_master;
    ros::master::init(remappings);
    while(ros::ok() && ros::master::check()==true){
        ros::spinOnce(); 
        loop_rate.sleep();
    }

}

My problem here is that there's no message when i read the /multimaster/chatter topic.

answered 2020-01-22 09:11:22 -0500

Joe28965

1124 ●3 ●73 ●28

Well first of all, you publish at /multimaster/chatter and you're saying you get nothing while listening to /multimaster_chatter which are in fact different topics.

Another problem could be that there is never anything published at /points_map so the callback function is never called.

The third option I can think of is that chat_ isn't properly defined in your class and is therefore not the same variable in your constructor as your callback function.

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Hi, thanks for you reply. I'm sorry my mistake, I'm also listening in /multimaster/chatter. But I can get the message in the callback function, the problem is that when I published the message to /multimaster/chatter topic.

crazyRan ( 2020-01-22 20:10:54 -0500 )edit

okay, then there are a couple of options

First, what I originally said as the third option, where do you create the variable chat_

Also, in your class foreignTopic you use the nodehandle n where do you create that one? Do you initialise ROS in your class? Do you somewhere after that call `n = new ros::NodeHandle();' to make sure the nodehandle is actually properly connected to ROS?

If your callback function is getting called, I would suspect your nodehandle isn't working correctly, could you also post the header file of foreignTopic and anything else that happens in this class, if you need more help

Joe28965 ( 2020-01-23 02:25:35 -0500 )edit

Hi, sorry for late reply. Thank you for your response. I fixed it already, but i didn't know what exactly the problem. Thank you so much!

crazyRan ( 2020-02-18 20:19:54 -0500 )edit

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