# Connection refused to the Ubuntu VM when using roswtf

The following is the result of the command roswtf, after having launched roslaunch turtle_tf turtle_tf_demo.launch (and nothing else).

nbro@nbro-virtual-machine:~\$ roswtf
No package or stack in context
================================================================================
Static checks summary:

No errors or warnings
================================================================================
Beginning tests of your ROS graph. These may take awhile...
analyzing graph...
... done analyzing graph
running graph rules...
ERROR: connection refused to [http://nbro-virtual-machine:34235/]
... done running graph rules
running tf checks, this will take a second...
... tf checks complete

Online checks summary:

Found 1 warning(s).
Warnings are things that may be just fine, but are sometimes at fault

WARNING The following node subscriptions are unconnected:
* /turtle_pointer:
* /tf_static

Found 3 error(s).

ERROR Could not contact the following nodes:
* /turtlesim

ERROR The following nodes should be connected but aren't:
* /teleop->/turtlesim (/turtle1/cmd_vel)

ERROR Errors connecting to the following services:
* service [/turtlesim/get_loggers] appears to be malfunctioning: Unable to communicate with service [/turtlesim/get_loggers], address [rosrpc://nbro-virtual-machine:55709]
* service [/turtlesim/set_logger_level] appears to be malfunctioning: Unable to communicate with service [/turtlesim/set_logger_level], address [rosrpc://nbro-virtual-machine:55709]


I am trying to understand why I am getting these errors. I first have a "connection refused" to http://nbro-virtual-machine:34235/, but I am executing this command from the same machine the nodes (e.g. /turtlesim) are running.

The second error says

ERROR Could not contact the following nodes:
* /turtlesim


However, rosnode list tells me the /turtlesim is running.

I have seen other posts with similar errors. I decided to close all the terminals, including the one which launched roscore. I executed roswtf again, after roslaunch turtle_tf turtle_tf_demo.launch, and now I don't have the errors above anymore, but just a warning:

WARNING The following node subscriptions are unconnected:
* /turtle_pointer:
* /tf_static


What's happening? Why did roswtf think that certain nodes (e.g. /teleop) were supposed to be connected (to what? to the master?), even though some of them were not connected but some were?

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I doubt the fact that you're running in a VM has anything to do with this, and "the Ubuntu VM" is also a bit of a misnomer. It's a regular VM, it just happens to be running Ubuntu.

( 2018-04-06 13:50:33 -0500 )edit

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I decided to close all the terminals, including the one which launched roscore. I executed roswtf again, after roslaunch turtle_tf turtle_tf_demo.launch, and now I don't have the errors above anymore, but just a warning

[..]

What's happening? Why did roswtf think that certain nodes (e.g. /teleop) were supposed to be connected (to what? to the master?), even though some of them were not connected but some were?

Most likely the master that was still running maintained some stale information, which caused roswtf to conclude that certain nodes should be on-line while they weren't. The TCP ports it tries to connect to would then be closed, resulting in the errors you show.

See #q285530 for a related question.

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For this part,

I executed roswtf again, after roslaunch turtle_tf turtle_tf_demo.launch, and now I don't have the errors above anymore, but just a warning:

WARNING The following node subscriptions are unconnected:
* /turtle_pointer:
* /tf_static


What's happening? Why did roswtf think that certain nodes (e.g. /teleop) were supposed to be connected (to what? to the master?), even though some of them were not connected but some were?

this isn't an issue, besides it's just a warning. See #q115591. For the case of turtle_tf specifically, TransformListener is used in this line in the code used to run turtle_pointer node.

Update: I found this warning confusing, so filed a ticket.

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