The ROS nodes can write or read data that has a different type. The types of data are described using a simplified message description language, also called ROS messages. These datatype descriptions can be used to generate source code for the appropriate message type in different target languages.
The data type description of ROS messages is stored in .msg files in the msg subdirectory of a ROS package. Even though the ROS framework provides a large set of robotic-specific messages already implemented, developers can define their own message type inside their nodes.
The message definition can consist of two types: fields and constants. The field is split into field types and field names. The field type is the data type of the ...
