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I am using Ubuntu 14.04LTS with Indigo ROS and an Arduino Mega 2560. When I run the command rosrun rosserial_python serial_node.py _port:=/dev/ttyACM0 _baud:=115200, I faced some connection problems first this command was working normally and the serial connection was connected successfully with the Arduino. suddenly after restart my PC the following Error was appear "socket.error: [Errno 111] Connection refused" and serial connection didn't established.

The following codes i write it by sequence :

> sudo usermod -a -G dialout wael
> sudo chmod a+rw /dev/ttyACM0
> rosrun rosserial_python serial_node.py _port:=/dev/ttyACM0 _baud:=115200

The following error appear

Traceback (most recent call last):
  File "/opt/ros/indigo/lib/rosserial_python/serial_node.py", line 46, in <module>
  File "/opt/ros/indigo/lib/python2.7/dist-packages/rospy/client.py", line 323, in init_node
    _init_node_params(argv, name)
  File "/opt/ros/indigo/lib/python2.7/dist-packages/rospy/client.py", line 186, in _init_node_params
    set_param(rosgraph.names.PRIV_NAME + param_name, param_value)
  File "/opt/ros/indigo/lib/python2.7/dist-packages/rospy/client.py", line 504, in set_param
    _param_server[param_name] = param_value #MasterProxy does all the magic for us
  File "/opt/ros/indigo/lib/python2.7/dist-packages/rospy/msproxy.py", line 148, in __setitem__
    self.target.setParam(rospy.names.get_caller_id(), rospy.names.resolve_name(key), val)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1233, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1587, in __request
  File "/usr/lib/python2.7/xmlrpclib.py", line 1273, in request
    return self.single_request(host, handler, request_body, verbose)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1301, in single_request
    self.send_content(h, request_body)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1448, in send_content
  File "/usr/lib/python2.7/httplib.py", line 975, in endheaders
  File "/usr/lib/python2.7/httplib.py", line 835, in _send_output
  File "/usr/lib/python2.7/httplib.py", line 797, in send
  File "/usr/lib/python2.7/httplib.py", line 778, in connect
    self.timeout, self.source_address)
  File "/usr/lib/python2.7/socket.py", line 571, in create_connection
    raise err
socket.error: [Errno 111] Connection refused

What can i do please to solve this problem?

Originally posted by Wael on ROS Answers with karma: 36 on 2016-11-17

Post score: 0

Original comments

Comment by gvdhoorn on 2016-11-17:
Have you set ROS_MASTER_URI or ROS_IP or ROS_HOSTNAME to something yourself? Are you on a DHCP network and could your IP have changed?


1 Answer 1


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The problem was in the ROS_MASTER_URI , it was not activated. After activating it the problem solved. Thank you for your support.

Originally posted by Wael with karma: 36 on 2016-11-17

This answer was ACCEPTED on the original site

Post score: 2

Original comments

Comment by shawnysh on 2017-01-12:
Thanks for your comment, it helps.

Comment by himS1234 on 2018-06-12:
How to activate it?

Comment by Carls on 2020-04-28:
Just type 'roscore'


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