Hey there,

I am right now trying, to run parallel simulations on my PC, all having one rosmaster and one corresponding simulation running. Here, I was no problem to open more than one Gazebo simulation. My problem lies in having more than one rosmaster on different ports.

I am using the multimaster_fkie package and did the following for my second terminal for the second rosmaster and simulation (the first one is running on port 11311):

tab 1: roscore -p 11312

tab 2:
export ROS_MASTER_URI=http://localhost:11312

rosrun master_discovery_fkie master_discovery _mcast_group:=224.0.0.251

Here, the following error occurs when I do the rosrun command:

[INFO] [1569575731.826636]: Create multicast socket at ('224.0.0.251', 11511)
[FATAL] [1569575731.827075]: Unable to bind multicast to interface: 224.0.0.251, check that it exists: [Errno 98] Address already in use
[ERROR] [1569575731.827957]: Traceback (most recent call last):
  File "<string>", line 108, in main
  File "/home/ifl/catkin_ws/src/multimaster/fkie_master_discovery/src/fkie_master_discovery/master_discovery.py", line 588, in __init__
    self._init_socket(True)
  File "/home/ifl/catkin_ws/src/multimaster/fkie_master_discovery/src/fkie_master_discovery/master_discovery.py", line 620, in _init_socket
    self.socket = DiscoverSocket(self.mcast_port, self.mcast_group, send_mcast=self._send_mcast, listen_mcast=self._listen_mcast)
  File "/home/ifl/catkin_ws/src/multimaster/fkie_master_discovery/src/fkie_master_discovery/udp.py", line 202, in __init__
    self.bind((to_group, port))
  File "/home/ifl/anaconda2/lib/python2.7/socket.py", line 228, in meth
    return getattr(self._sock,name)(*args)
error: [Errno 98] Address already in use

Error while start master_discovery: [Errno 98] Address already in use

I tried both, roscore -p 11312 and roscore --port=11312 to get the changed port. But the problem remains..

Do you guys have a solution for that problem?

Thanks!