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ERROR: Unable to communicate with master!

asked 2012-03-20 19:59:35 -0500

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Hello. I'm Korean student. So i cannot speak English very well. Thank you for your consideration.

I am setting Turtlebot on my netbook and my notebook (Network Connection) http://www.ros.org/wiki/Robots/TurtleBot/Network%20Setup

My netbook is TurtleBot laptop. My notebook is Workstation.

I am able to ping each other. One is 192.168.0.67 and another is 192.168.0.63

and i can see "echo $ROS_MASTER_URI" and "echo $ROS_HOSTNAME". "turtlebot start/running, process 16951" also.

but when i enter the command "rostopic list", i see "ERROR: Unable to communicate with master!"

I don't know why.. because when i set "Network Setup" first time, there work correctly.. but after the reboot, i cannot do anything..

Please help me ~.~

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could you post the output of "echo $ROS_MASTER_URI" and "echo $ROS_HOSTNAME"? Many times when I get this error, it's because of settings error

weiin gravatar image weiin  ( 2012-03-20 23:43:10 -0500 )edit

my notebook.. ROS_MASTER_URI == http://192.168.0.67:11311 and ROS_HOSTNAME == 192.168.0.63 and my netbook.. ROS_MASTER_URI == http://192.168.0.67:11311 and ROS_HOSTNAME == 192.168.0.67

SanghaNam gravatar image SanghaNam  ( 2012-03-21 18:40:23 -0500 )edit

IP of my notebook is 192.168.0.64 (turtlebot-workspace) IP of my netbook is 192.168.0.67 (turtlebot-robot)

SanghaNam gravatar image SanghaNam  ( 2012-03-21 18:42:35 -0500 )edit

i think "roscore" is right.. but.. i cannot start turtlebot service.. when i enter the command "sudo service turtlebot start", i can see the message "rustlebot start/running, process 3326" and i enter the command "rostopic list", i can see the message only "/rosout" and "/rosout_agg" i don't know..

SanghaNam gravatar image SanghaNam  ( 2012-03-21 18:42:49 -0500 )edit

not sure if it's a typo, but in your comments, your turtlebot-workspace IP 192.168.0.64 does not match the notebook's ROS_HOSTNAME 192.168.0.63 so that could be why it's not working correctly

weiin gravatar image weiin  ( 2012-03-22 15:01:39 -0500 )edit

oh sorry. i was miss typing.. t.t

SanghaNam gravatar image SanghaNam  ( 2012-03-23 03:04:34 -0500 )edit

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answered 2012-03-20 22:54:30 -0500

michikarg gravatar image

I am not familiar with the turtlebot setup, but this typically means that you do not have a roscore running. Open a new shell, type "roscore" and try again...

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answered 2012-03-21 22:08:57 -0500

bit-pirate gravatar image

안녕하세요!

I'm also not familiar with the turtlebot environment, but working with multiple robots and workstation.

First, when you start the turtlebot process on the turtlebot (aka netbook), do you see the desired topics (do 'rostopic list' on the netbook)? If your network is properly configured, you should see the same list of topics on your workstation (notebook).

Now, based on your comments, the above doesn't work for you. Have you gone through the instructions here: http://www.ros.org/wiki/ROS/NetworkSetup? These instruction are for a general ROS network setup and are more extensive than the ones for the turtlebot. Section "2. Name resolution" might be helpful for you. Try setting the ROS_IP in addition to ROS_MASTER_URI. That often helps me when I have problems with the 2-way communication robot <-> workstation.

PS: I seldom use ROS_HOSTNAME. This requires that your machine can resolve that name, e.g. you need DNS server working or the required entries set in /etc/hosts (assuming your are running linux).

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answered 2012-03-21 22:39:19 -0500

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Hi, My answer here might help you check your network setup. http://answers.ros.org/question/29983/turtlebot_teleop-not-working-properly

Hope it helps, Karthik

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Asked: 2012-03-20 19:59:35 -0500

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Last updated: Mar 21 '12