rostopic list return topics, but not able to echo topic

Question

Hello,

My configuration looks like:

Beaglebone black with GPS + laptop. Both running Ubuntu 14.04 and ROS indigo.

I would like to run roscore at laptop and node gpsd_client at beaglebone. I set following variables: At laptop (ip 192.168.7.1):

export ROS_IP=192.168.7.1
export ROS_HOSTNAME=192.168.7.1
export ROS_MASTER_URI=http://192.168.7.1:11311

At beaglebone (ip 192.168.7.2):

export ROS_IP=192.168.7.2
export ROS_HOSTNAME=192.168.7.1
export ROS_MASTER_URI=http://192.168.7.1:11311

I'm able to ping each other. I'm able to do rostopic list from both. But I'm not able to do rostopic echo fix.

roswtf give following error msg:

Loaded plugin tf.tfwtf
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://192.168.7.1:41219/]
... done running graph rules

Online checks summary:

Found 3 error(s).

ERROR Could not contact the following nodes:
 * /gpsd_client

ERROR The following nodes should be connected but aren't:
 * /gpsd_client->/rosout (/rosout)

ERROR Errors connecting to the following services:
 * service [/gpsd_client/get_loggers] appears to be malfunctioning: Unable to communicate with service [/gpsd_client/get_loggers], address [rosrpc://192.168.7.1:58483]
 * service [/gpsd_client/set_logger_level] appears to be malfunctioning: Unable to communicate with service [/gpsd_client/set_logger_level], address [rosrpc://192.168.7.1:58483]

I see error

ERROR The following nodes should be connected but aren't:
 * /gpsd_client->/rosout (/rosout)

but unfortunately I don't now how should I fix it.

I tried another configuration, when roscore was running at beaglebone with gpsd_client, and do echo from laptop - this is working without any problem. Just problem apear when I run roscore at one machine and node in another.

I hope that my problem is trivial to fix and I'm just missing some setting.

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Originally posted by darkom on ROS Answers with karma: 3 on 2015-08-26

Post score: 0

Answer 1

At laptop (ip 192.168.7.1):

export ROS_IP=192.168.7.1

export ROS_HOSTNAME=192.168.7.1
export ROS_MASTER_URI=http://192.168.7.1:11311

At beaglebone (ip 192.168.7.2):

export ROS_IP=192.168.7.2

export ROS_HOSTNAME=192.168.7.1
export ROS_MASTER_URI=http://192.168.7.1:11311

Is that an actual copy/paste? Because you have ROS_HOSTNAME set to the same IP on both machines, which is not what you want I guess.

Also, you should not / don't need to set both ROS_IP and ROS_HOSTNAME at the same time. Just setting ROS_IP should be enough (but make sure to set it to the correct IP). From the wiki/ROS/EnvironmentVariables - ROS_IP/ROS_HOSTNAME page:

[..] The options are mutually exclusive, if both are set ROS_HOSTNAME will take precedence. Use ROS_IP if you are specifying an IP address, and ROS_HOSTNAME if you are specifying a host name. [..]

If you then have ROS_HOSTNAME set to an incorrect IP, things will probably not work.

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Originally posted by gvdhoorn with karma: 86574 on 2015-08-26

This answer was ACCEPTED on the original site

Post score: 2

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Original comments

Comment by darkom on 2015-08-27:
Thank you so much. Now it is working just great.