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Ssh error - should I change

asked 2018-07-19 10:45:24 -0500

AmateurHour gravatar image

updated 2018-07-20 12:17:36 -0500

Hello! I am attempting to ssh into a turtlebot3 from my ubuntu 16.04 and launch turtlebot_bringup after that. Although the ssh is successful, I am getting the following error when the script tries to start the nodes:

error launching on [, uri http://turtlebot:34746/]: No route to host
Launch of the following nodes most likely failed: rosserial_python/, hls_lfcd_lds_driver/hlds_laser_publisher, turtlebot3_bringup/turtlebot3_diagnostics

Here's my launch script:

<!-- ssh into bot and launch bringup -->    
<!-- Robot1 -->
   <!-- may need to remove ns from group tag-->
   <group ns="bot1">
       <param name="tf_prefix" value="bot1_tf" />
       <!-- Machine tag applies to any nodes/includes that come after it in the same scope -->
       <!-- default=true sets this machine as the default to assign nodes to within the scope -->
       <machine name="bot1" address="10.1.xx.xx" user="xxxxx" password="xxxxxx" default="true" env-loader="~/catkin_ws/devel/"/>

       <!-- Instead of including turtlebot3_robot.launch, include everything that is in it-->
       <!-- <include file="$(find turtlebot3_bringup)/launch/turtlebot3_robot.launch"/> -->
       <include file="$(find turtlebot3_bringup)/launch/turtlebot3_core.launch"/>
       <include file="$(find turtlebot3_bringup)/launch/turtlebot3_lidar.launch"/>        
       <!-- add machine name to diagnostics? machine="bot1" -->
       <node machine="bot1" pkg="turtlebot3_bringup" type="turtlebot3_diagnostics" name="turtlebot3_diagnostics" output="screen" />

Do I need to edit the file or something along those lines? I am using the standard generated one from catkin_ws/devel. Thanks! as it stands currently (all values taken directly from ssh printenv):

#!/usr/bin/env sh
# generated from catkin/cmake/templates/

if [ $# -eq 0 ] ; then
  /bin/echo "Usage: COMMANDS"
  /bin/echo "Calling without arguments is not supported anymore. Instead spawn a subshell and source a setup file manually."
  exit 1

# ensure to not use different shell type which was set before

# source from same directory as this file
_CATKIN_SETUP_DIR=$(cd "`dirname "$0"`" > /dev/null && pwd)

export ROS_ROOT=/opt/ros/kinetic/share/ros
export ROS_MASTER_URI=http://10.1.xx.xx:11311
export PYTHONPATH=/home/raspberry/catkin_ws/devel/lib/python2.7/dist-packages:/opt/ros/kinetic/lib/python2.7/dist-packages
export ROS_PACKAGE_PATH=/home/raspberry/catkin_ws/src:/opt/ros/kinetic/share
export ROS_ETC_DIR=/opt/ros/kinetic/etc/ros
export ROS_IP=10.1.xx.xx
source ~/catkin_ws/devel/setup.bash
source /opt/ros/kinetic/setup.bash
export PATH=/home/raspberry/bin:/home/raspberry/.local/bin:/opt/ros/kinetic/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
export ROS_WORKSPACE=/home/catkin_ws

exec "$@"
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Have you tried to individually launch the different node listed from the turtlebot ? Then from your PC ? Also try to check the permissions of your sensors/actuators : ls -l /dev/

Delb gravatar image Delb  ( 2018-07-20 02:27:02 -0500 )edit

Hi there, and thanks for your reply! I used the command suggested and saw that everything on the turtlebot seems to have root access. I did notice that the ports being access for the launch, such as /dev/ttyACM0 and /dev/ttyUSB0 , also have "dailout" next to root instead of root root like the others

AmateurHour gravatar image AmateurHour  ( 2018-07-20 10:14:26 -0500 )edit

Dialout means that toi have access to the input from/dev si that's normal Have you tried to launch each node separatly ?

Delb gravatar image Delb  ( 2018-07-20 10:20:47 -0500 )edit

I have confirmed that I can launch all the nodes individually after ssh-ing into the bot. Also , instead of connection refused , I am now getting a No route to host error. (question updated to reflect this)

AmateurHour gravatar image AmateurHour  ( 2018-07-20 10:49:16 -0500 )edit

Okay so it's probably @ahendrix 's first suggestion, can you print the value of ROS_MASTER_URIand ROS_HOSTNAME from your pc and the turtlebot please ? (Using echo $ROS_MASTER_URI

Delb gravatar image Delb  ( 2018-07-20 11:57:26 -0500 )edit

echo ROS_MASTER_URI returns the same value for bot and pc, and as in ROS_HOSTNAME returns nothing, and I have specified ROS_IP in my file as stated in the bot's printenv. ROS_IP is the same as in the machine tag of my launch file. I edited the question to include, Thank you!!

AmateurHour gravatar image AmateurHour  ( 2018-07-20 12:10:45 -0500 )edit

Got it figured out! Turns out it was a simple i.p. change that needed to be made in /etc/hosts. Thank you so much for all your suggestions! If anyone else is looking for this, the exact command is sudo nano /etc/hosts

AmateurHour gravatar image AmateurHour  ( 2018-07-20 13:54:40 -0500 )edit

Can you detail what you changed exactly in /etc/hosts to help other people ?

Delb gravatar image Delb  ( 2018-07-20 14:00:36 -0500 )edit

1 Answer

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answered 2018-07-19 20:25:48 -0500

ahendrix gravatar image

Connection refused means that it couldn't establish any connection to the remote machine. There are a few common things that could cause this:

  • Incorrect IP address
  • SSH server isn't running
  • No network connection between computers (cable unplugged, wifi down, etc)

I would start by trying to ssh to the remote machine manually by running:

ssh xxxxx@10.1.xx.xx

Establish that SSH works with that command before you try to troubleshoot roslaunch further.

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Thank you so much for your answer! Yes, ssh works perfectly, where user is the same as what I have stated in my machine tag. Is it possible that I have done the machine tag wrong?

AmateurHour gravatar image AmateurHour  ( 2018-07-19 21:18:35 -0500 )edit

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Asked: 2018-07-19 10:45:24 -0500

Seen: 833 times

Last updated: Jul 20 '18