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rospy.wait_for_message just hangs

asked 2018-08-07 10:59:43 -0500

Marc_Chen gravatar image

updated 2018-08-07 12:28:21 -0500

jayess gravatar image

there is no exception or anything, rospy.wait_for_message just hangs, and no result is returned, and no subsequent code is executed. running

rostopic echo /my_topic

is able to yield result. Someone can provide an example of how to use wait_fo_message?

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answered 2018-08-07 12:26:53 -0500

jayess gravatar image

updated 2019-07-09 16:05:54 -0500

Take a look at the documentation. Or, if you look at the source for the wait_for_message function, you'll see that you can specifiy a timeout. If that timeout is exceeded then an exception will be raised (I removed the parts that aren't necessary for the question)

def wait_for_message(topic, topic_type, timeout=None):
    """
    ...

    @param timeout: timeout time in seconds
    @type  timeout: double
    ...
    @raise ROSException: if specified timeout is exceeded
    """

So, just call the function like this

rospy.wait_for_message(my_topic, MyMessage, my_timeout)

and if my_timeout is exceeded a ROSException will be raised.

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Comments

No need to go to the source, just read the documentation.

gvdhoorn gravatar imagegvdhoorn ( 2018-08-07 13:48:34 -0500 )edit
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answered 2019-07-09 15:34:45 -0500

rfn123 gravatar image

I had the same problem, using it like this:

rospy.wait_for_message("ar_pose_marker",AlvarMarkers)

The problem was that I missed a rospy.spin() in the whole Python script, because I did not intend to create a ROS node. However the missing rospy.spin was causing rospy not iterating through the message queues, thus waiting forever even if the topic actually publishes something.

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Asked: 2018-08-07 10:59:43 -0500

Seen: 426 times

Last updated: Jul 09