ROS problems (topic types do not match, topic datatype/md5sum not match, MSG XXX have changed. rerun cmake)

1. topic types Mismatch

Use roslaunch command

roslaunch carla_ros_bridge carla_ros_bridge_with_example_ego_vehicle.launch

Start the official demo after , Attempt to write by hand Python Script to control the vehicle , But there are errors reported below ：

Could not process inbound connection: topic types do not match: 
[carla_msgs/CarlaEgoVehicleControl] vs. [topic_demo/CarlaEgoVehicleControl]

Obviously topic Type mismatch , We need to give carla_msgs/CarlaEgoVehicleControl Send control command , So our topic Should also be carla_msgs .

resolvent ：

• stay ~/catkin_ws Create a new directory carla_msgs Folder and then re execute catkin_make command

2. topic datatype/md5sum atypism

problem 1 After the solution, the following errors are reported

Could not process inbound connection: Client [/carla_ros_bridge] 
wants topic [/carla/ego_vehicle/vehicle_control_cmd] to have datatype/md5sum 
[carla_msgs/CarlaEgoVehicleControl/e5b57fc698c12ff4c20a5fc71fba832f], 
but our version has [carla_msgs/CarlaEgoVehicleControl/919d1c0732720a839958ff82b9ba0dcd] 
Dropping connection.

Because we modified the topic Corresponding msg perhaps srv file , Leading to both MD5 Inconsistent values .

resolvent ：

• Will be original msg perhaps srv Copy the file and put it in your current Python Project package Under the table of contents , Then execute again catkin_make .

3. message/service xxx have changed. Please rerun cmake.

problem 1 and 2 After solving, proceed to catkin_make An error is reported when ordering ：

The dependencies of the message/service 'carla_msgs/CarlaEgoVehicleControl' have changed. Please rerun cmake.
carla_msgs/CMakeFiles/_carla_msgs_generate_messages_check_deps_CarlaEgoVehicleControl.dir/build.make:57: 
recipe for target 'carla_msgs/CMakeFiles/_carla_msgs_generate_messages_check_deps_CarlaEgoVehicleControl' failed

Obviously because of CarlaEgoVehicleControl.msg After the document is changed, it needs to be re cmake.

resolvent ：

• Delete workspace ~/catkin_ws in devel and build The corresponding project directory file under the directory , Like my catalog carla_msgs .（build The directory contains include and lib Catalog ）

Reference resources ：https://answers.ros.org/question/138731/catkin_make-clean/