Hi.

I am new to Gazebo and ROS and i want to control the example Cessna plane in Gazebo using ROS.

I am starting the Gazebo using following command:

gazebo --verbose worlds/cessna_demo.world

When i do

gz topic -l

I have all related topics with cessna plane and simulation environment but when i do

rostopic list

I get the following error in ROS terminal

Traceback (most recent call last):
File "/opt/ros/melodic/bin/rostopic", line 35, in rostopic.rostopicmain() File "/opt/ros/melodic/lib/python2.7/dist-packages/rostopic/init.py", line 2119, in rostopicmain rostopiccmdlist(argv) File "/opt/ros/melodic/lib/python2.7/dist-packages/rostopic/init.py", line 2059, in _rostopiccmdlist exitval = _rostopiclist(topic, verbose=options.verbose, subscribersonly=options.subscribers, publishersonly=options.publishers, groupbyhost=options.hostname) or 0
File "/opt/ros/melodic/lib/python2.7/dist-packages/rostopic/init.py", line 1225, in rostopiclist pubs, subs = gettopiclist(master=master) File "/opt/ros/melodic/lib/python2.7/dist-packages/rostopic/init.py", line 1164, in gettopiclist state = master.getSystemState() File "/opt/ros/melodic/lib/python2.7/dist-packages/rosgraph/masterapi.py", line 481, in getSystemState return self.succeed(self.handle.getSystemState(self.callerid)) File "/usr/lib/python2.7/xmlrpclib.py", line 1243, in call return self.send(self.name, args) File "/usr/lib/python2.7/xmlrpclib.py", line 1602, in request verbose=self.verbose File "/usr/lib/python2.7/xmlrpclib.py", line 1283, in request return self.singlerequest(host, handler, requestbody, verbose) File "/usr/lib/python2.7/xmlrpclib.py", line 1316, in singlerequest return self.parseresponse(response) File "/usr/lib/python2.7/xmlrpclib.py", line 1487, in parseresponse p.feed(data) File "/usr/lib/python2.7/xmlrpclib.py", line 558, in feed self.parser.Parse(data, 0) xml.parsers.expat.ExpatError: syntax error: line 1, column 0

And following error in Gazebo terminal:

[Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty [Err] [Connection.hh:267] Header is empty Master Unknown message type[] From[47356] Master Unknown message type[] From[47356] Master Unknown message type[] From[47356] [libprotobuf ERROR google/protobuf/messagelite.cc:118] Can't parse message of type "gazebo.msgs.Packet" because it is missing required fields: stamp, type, serializeddata Master Unknown message type[] From[47356] Master Unknown message type[] From[47356]

What am i missing?

Thanks...