Gazebo Custom Message Doesn't Show In Topic Echo

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Introduction

Gazebo is a powerful open-source robotics simulator that provides a wide range of tools and features for simulating and testing robotic systems. One of the key features of Gazebo is its ability to create and publish custom messages, which can be used to communicate between different components of a robotic system. However, sometimes creating a new custom message in Gazebo can be a challenging task, especially when it comes to getting it to show up in the topic echo. In this article, we will explore the common issues that can cause a custom message to not show up in the topic echo and provide some tips and tricks for troubleshooting and resolving these issues.

Understanding Custom Messages in Gazebo

Before we dive into the troubleshooting process, it's essential to understand how custom messages work in Gazebo. Custom messages are created using Protocol Buffers (protobuf), a language-neutral, platform-neutral, extensible mechanism for serializing structured data. In Gazebo, custom messages are defined in a .proto file, which contains the message definition in protobuf syntax.

Creating a New Custom Message in Gazebo

To create a new custom message in Gazebo, you need to follow these steps:

  1. Create a new .proto file: Create a new file with a .proto extension, for example, my_message.proto.
  2. Define the message: Define the message in the .proto file using protobuf syntax. For example:
syntax = "proto3";

package gnss_sim.msgs;


import "gz/msgs/header.proto";


message MyMessage {
string data = 1;
}

  1. Compile the .proto file: Compile the .proto file using the protoc compiler to generate the message code. For example:
protoc --cpp_out=. my_message.proto
  1. Create a new message class: Create a new C++ class that inherits from the generated message class. For example:
#include "my_message.pb.h"

class MyMessage : public gnss_sim::msgs::MyMessage {
// ...
};

  1. Publish the message: Publish the message using the ros::Publisher class. For example:
#include <ros/ros.h>

int main(int argc, char **argv) 
ros:init(argc, argv, "my_publisher");
ros::NodeHandle nh;
ros::Publisher pub = nh.advertise<gnss_sim::msgs::MyMessage>("my_topic", 10);
// ...

Troubleshooting Custom Message Issues

Now that we have created a new custom message in Gazebo, let's troubleshoot some common issues that can cause it to not show up in the topic echo.

Issue 1: Message Not Published

If the message is not published, it will not show up in the topic echo. To troubleshoot this issue, check the following:

  • Check the publisher: Make sure that the publisher is running and publishing the message. You can check the publisher's output to see if it's publishing the message.
  • Check the topic: Make sure that the topic is correctly defined and that the publisher is publishing to the correct topic.
  • Check the message type: Make sure that the message type is correctly defined and that the publisher is publishing the correct message type.

Issue 2: Message Not Subscribed

If the message is published but not subscribed, it will not show up in the topic echo. To troubleshoot this issue, check the following:

  • Check the subscriber: Make sure that the subscriber is running and subscribed to the topic.
  • Check the topic: Make sure that the topic is correctly defined and that the subscriber is subscribed to the correct topic.
  • Check the message type: Make sure that the message type is correctly defined and that the subscriber is subscribed to the correct message type.

Issue 3: Message Not Displayed

If the message is published and subscribed but not displayed, it may be due to a display issue. To troubleshoot this issue, check the following:

  • Check the display settings: Make sure that the display settings are correctly configured to display the message.
  • Check the message format: Make sure that the message format is correctly defined and that the display settings are configured to display the message in the correct format.

Conclusion

Introduction

In our previous article, we explored the common issues that can cause a custom message to not show up in the topic echo in Gazebo. In this article, we will provide a Q&A section to help you troubleshoot and resolve these issues.

Q: I created a new custom message in Gazebo, but it doesn't show up in the topic echo. What should I do?

A: First, check the publisher to make sure it's running and publishing the message. Then, check the topic to ensure it's correctly defined and that the publisher is publishing to the correct topic. Finally, check the message type to ensure it's correctly defined and that the publisher is publishing the correct message type.

Q: I'm using a ROS (Robot Operating System) node to publish my custom message, but it doesn't show up in the topic echo. What could be the issue?

A: There could be several issues with your ROS node. Check the following:

  • ROS node not running: Make sure the ROS node is running and publishing the message.
  • Topic not defined: Ensure the topic is correctly defined in the ROS node.
  • Message type not defined: Ensure the message type is correctly defined in the ROS node.
  • ROS node not subscribed: Ensure the ROS node is subscribed to the topic.

Q: I'm using a Gazebo plugin to publish my custom message, but it doesn't show up in the topic echo. What could be the issue?

A: There could be several issues with your Gazebo plugin. Check the following:

  • Plugin not loaded: Ensure the plugin is loaded and running.
  • Topic not defined: Ensure the topic is correctly defined in the plugin.
  • Message type not defined: Ensure the message type is correctly defined in the plugin.
  • Plugin not publishing: Ensure the plugin is publishing the message.

Q: I'm using a custom message type that's not defined in the Gazebo message library. How can I define a custom message type?

A: To define a custom message type, you need to create a new .proto file that defines the message type. Then, compile the .proto file using the protoc compiler to generate the message code. Finally, include the generated message code in your plugin or ROS node.

Q: I'm using a custom message type that's defined in a separate .proto file. How can I include it in my plugin or ROS node?

A: To include a custom message type defined in a separate .proto file, you need to import the .proto file in your plugin or ROS node. Then, compile the .proto file using the protoc compiler to generate the message code. Finally, include the generated message code in your plugin or ROS node.

Q: I'm using a custom message type that's defined in a separate library. How can I include it in my plugin or ROS node?

A: To include a custom message type defined in a separate library, you need to link the library in your plugin or ROS node. Then, include the header file of the library in your plugin or ROS node.

Conclusion

In this Q&A article, we provided answers to common questions related to custom messages in Gazebo. We hope this article helps you troubleshoot and resolve issues related to custom messages in Gazebo. Remember to always check the publisher, topic, and message type to ensure that the message is published and subscribed correctly.

Additional Resources

  • Gazebo documentation: The official Gazebo documentation provides detailed information on creating and publishing custom messages in Gazebo.
  • ROS documentation: The official ROS documentation provides detailed information on creating and publishing custom messages in ROS.
  • Gazebo message library: The Gazebo message library provides a set of pre-defined message types that can be used in Gazebo plugins and ROS nodes.

Troubleshooting Tips

  • Check the publisher: Make sure the publisher is running and publishing the message.
  • Check the topic: Ensure the topic is correctly defined and that the publisher is publishing to the correct topic.
  • Check the message type: Ensure the message type is correctly defined and that the publisher is publishing the correct message type.
  • Check the ROS node: Ensure the ROS node is running and subscribed to the topic.
  • Check the Gazebo plugin: Ensure the Gazebo plugin is loaded and running.