Every time a message is published for the given topic, the callback will be called with the message object.
||function with the following params: * message - the published message|
callService(request, callback, failedCallback)
Calls the service. Returns the service response in the callback.
||the ROSLIB.ServiceRequest to send|
||function with params: * response - the response from the service request|
||the callback function when the service call failed (optional). Params: * error - the error message reported by ROS|