Errors when using package

Error: Received error message in header... Dropping connection

Example:

• [ERROR] 1260927377.348922000: Received error message in header for connection to [TCPROS connection to [10.0.0.136:39531 on socket 17]]: [Client [/image_view_1260927377013984000] wants topic /image/compressed to have datatype/md5sum [sensor_msgs/Image/060021388200f6f0f447d0fcd9c64743], but our version has [sensor_msgs/CompressedImage/8f7a12909da2c9d3332d540a0977563f]. Dropping connection.]

Above that error you might see a warning:

• [ WARN] 1260927377.319546000: [image_transport] It looks like you are trying to subscribe directly to a transport-specific image topic '/image/compressed', in which case you will likely get a connection error. Try subscribing to the base topic '/image' instead with parameter ~image_transport set to 'compressed' (on the command line, _image_transport:=compressed). See http://ros.org/wiki/image_transport for details.

Solution:

• Are you subscribing to an image topic?

  • If the data type of the topic you remapping image to is not sensor_msgs/Image, ROS will detect the mismatch and drop the connection. For example:

    $ rostopic type image/compressed
    sensor_msgs/CompressedImage
    # Does not match sensor_msgs/Image

• Are you subscribing to a transport-specific subtopic? For example, image_view image:=camera/image/theora?

  • This is a corollary of the previous case; the data type of a transport-specific topic like camera/image/theora is not sensor_msgs/Image but rather some packet message type. If you want to view the base topic camera/image using theora streaming video, give the transport name as a separate argument:

    $ rosrun image_view image_view image:=camera/image theora

    That tells image_view to load the theora plugin to image_transport and subscribe to the appropriate subtopic.