Roslaunch API refusing connection

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Hi,

I'm having trouble using the roslaunch python api in my scripts, which is quite boring. According to http://wiki.ros.org/roslaunch/API%20U... I should be able to use roslaunch in python script, but I'm always having this error :

Traceback (most recent call last):
  File "roslaunchtest.py", line 9, in <module>
    launch = roslaunch.scriptapi.ROSLaunch()
  File "/opt/ros/hydro/lib/python2.7/dist-packages/roslaunch/scriptapi.py", line 61, in __init__
    uuid = master.getParam('/run_id')
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rosgraph/masterapi.py", line 206, in getParam
    return self._succeed(self.handle.getParam(self.caller_id, key))
  File "/usr/lib/python2.7/xmlrpclib.py", line 1224, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1578, in __request
    verbose=self.__verbose
  File "/usr/lib/python2.7/xmlrpclib.py", line 1264, in request
    return self.single_request(host, handler, request_body, verbose)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1292, in single_request
    self.send_content(h, request_body)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1439, in send_content
    connection.endheaders(request_body)
  File "/usr/lib/python2.7/httplib.py", line 954, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python2.7/httplib.py", line 814, in _send_output
    self.send(msg)
  File "/usr/lib/python2.7/httplib.py", line 776, in send
    self.connect()
  File "/usr/lib/python2.7/httplib.py", line 757, 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

Is it normal that the simplest code isn't working ? Or am I doing something wrong ? I'd like to find a solution for that, since I need to launch a few files, like the turtlebot minimal, 3d sensors, and autodocking script. If it's not possible in this way, is there a workaround ?

Thanks

Ray