Sensor-based messages are contained within the directory:
Defining Custom Messages
ROS messages are defined in
An automatic MD5 sum of the
.msg file is created and is checked when nodes try and publish/subscribe to topics. Nodes can only communicate when both the message type and MD5 sums match.
ROS messages may include a special header. This can contain a time stamp and frame ID.
If the message types are not the same, you will normally get a runtime error on launch similar to:
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