API to know if a node is alive?

rosnode

asked 2013-01-16 01:44:28 -0500

Daniel Pinyol
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I could run a system("rosnode ping -c1 /nodeName"), but this always return return code 0. I could grep the standard output of rosnode, but it sounds quite dirty.

thanks

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did you manage to find out a way to do that?

maero ( 2014-09-30 11:31:27 -0500 )edit

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answered 2013-01-16 04:07:11 -0500

thebyohazard
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I don't know why you're checking for existence, but if your node provides an action, you can wait for the server to start with waitForServer. You can also wait for a transform to become available with waitForTransform.

If you have other reasons, there's apparently a package, interface tester, that was designed to do this, but I can only find the tutorial, not the source. Maybe you'll have better luck finding it.

You could also use the rosnode api. It's in python, and there might be zombie nodes, but it should give you what you need.

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If your node provides an action _or a service_. Or you could even have it publish on /i_am_alive...

Mac ( 2013-01-16 05:50:49 -0500 )edit

The answer in #q164601 shows use of the rosnode api.

lucasw ( 2019-08-13 20:36:17 -0500 )edit

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answered 2013-01-16 05:25:30 -0500

Dan Lazewatsky
9115 ●79 ●103 ●160 http://dan.lazewatsky.com/

To extend on what @tbh said, if you're not using python, the internals of rosnode.rosnode_ping() shows you how pinging a node works. It's basically just doing a xmlrpc call asking for the node's PID and seeing if that succeeds.