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Error "Client wants topic A to have B, but our version has C. Dropping connection."

asked 2011-10-20 15:15:57 -0600

130s gravatar image

updated 2011-10-20 19:21:12 -0600

In my custom application using custom message, publisher node show the following message only once on its running console when subscriber starts. Both nodes keep running but it seems nothing occur after that.

error msg:

[ERROR] [1319162712.616980036]: Client [/clientNodeA] wants topic /server_msgs/Swarm 
to have datatype/md5sum [server_msgs/Swarm/6a727e7bfd7e4aadf9d23c4a779b268e], 
but our version has [geometry_msgs/Point/4a842b65f413084dc2b10fb484ea7f17]. 
Dropping connection.

Content of the custom message (/server_msgs/Swarm):

uint32 clockValue
geometry_msgs/Point[] crowds

Publisher node's code .cpp (partial)

Subscriber node's code .cpp

Running environment: Ubuntu 11.04, electric


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2 Answers

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answered 2011-10-20 15:48:52 -0600

joq gravatar image

Your publisher is advertising geomety_msgs/Point (line 15).

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@joq thank you. This was my bad careless mistake...
130s gravatar image 130s  ( 2011-10-20 19:20:37 -0600 )edit

Just to be clear (since this is the first google result for client wants topic to have datatype/md5sum), the error is that the publisher and subscriber on the same topic have differing message types.

lucasw gravatar image lucasw  ( 2014-01-30 06:47:10 -0600 )edit

I changed my custom message to have header in it. After that I keep getting this error.

[ERROR] [1552465010.096584454, 1550537307.791138420]: Client [/rostopic_21875_1552464987475] wants topic /3d_data to have datatype/md5sum [openpose_ros/PersonDetection_3d/bc1a43439603de5789cfba6300034ed3], but our version has [openpose_ros/PersonDetection_3d/a4ff6437cb65b2eb3d526e8df30d59ce]. Dropping connection.
Harsh2308 gravatar image Harsh2308  ( 2019-03-13 03:18:04 -0600 )edit

Make sure sender and receiver have the latest version with the header (maybe both need to pull the latest source and recompile if on different computers), and that they have sourced devel or install setup.bash where the new version was built (restarting a terminal as mentioned below will possibly do that).

lucasw gravatar image lucasw  ( 2019-03-13 11:34:23 -0600 )edit

answered 2016-05-11 11:15:16 -0600

aland_t gravatar image

For anyone else who gets this error, check the queue size. I had this error, but in my case it was caused by conflicting queue sizes between the publisher and subscriber.

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I had a similar non-obvious issue that went away when I restarted all of my terminal tabs. Using Terminator on an Ubuntu 16.04 machine

tarunuday gravatar image tarunuday  ( 2018-03-30 10:45:06 -0600 )edit

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Asked: 2011-10-20 15:15:57 -0600

Seen: 25,330 times

Last updated: May 11 '16