How to communicate between ROS machines through VPN

edit

I am working on a project which requires two machines comunicating through a VPN. At the moment I am trying to connect my PC to a remote server (through VPN as well), both have ROS kinetic installed, and I would like to run a simple listener/talker communication.

They are connected using openvpn, by means of a tun0 interface which gives respectively to the server and to the PC the addresses 10.8.0.1 and 10.8.0.2. Both the machines are able to ping each other, hence I assume that the VPN is working properly.

I run the following commands on the machines:

SERVER:

• Roscore:

  clear

  sudo -s

  cd ~/catkin_ws/

  catkin_make

  . ~/catkin_ws/devel/setup.bash

  export ROS_IP=10.8.0.1

  export ROS_MASTER_URI=http://10.8.0.1:11311

  roscore

• Listener

  clear

  sudo -s

  cd ~/catkin_ws/

  catkin_make

  . ~/catkin_ws/devel/setup.bash

  export ROS_IP=10.8.0.1

  export ROS_MASTER_URI=http://10.8.0.1:11311

  rosrun rospy_tutorials listener.py

PC:

• Talker

  clear

  cd ~/catkin_ws/

  catkin_make

  . ~/catkin_ws/devel/setup.bash

  export ROS_IP=10.8.0.2

  export ROS_MASTER_URI=http://10.8.0.1:11311

  rosrun rospy_tutorials talker.py

Note that I have to instance every time the ROS_IP and the ROS_MASTER_URI since I open a new terminal.

However, the PC is not able to find the ROS master running on the server.

Therefore I would like to point out whether this is a problem of wrong ROS configuration or a VPN problem, maybe I need to set some IP forwarding rules.

Thanks for you help.