We don't have any networking guides for ROS 2 yet.
However, ROS 2 uses DDS by default, so you could draw on those resources to get help configuring your network to allow DDS traffic. For both ROS 1 and ROS 2, communication over the internet has two challenges, discovery and peer-to-peer communication.
tl;dr I'd use VPN between the remote computers, and set it up to forward multicast UDP as well.
discovery
But, for the case you specifically laid out, it will be difficult. DDS does discovery over UDP multicast and UDP unicast. So doing discovery across the internet is not going to work that way. This is because UDP multicast will not work over the internet as far as I know.
In ROS 1 you could solve this by making the ROS master publicly accessible on the internet, and pointing the nodes on the remote machine to the public IP and port for the machine running the ROS master. However, the nodes still communicate peer-to-peer.
In ROS 2, I don't know of a generic solution, but individual DDS implementations may have tools for relaying discovery information across the internet. Though I don't think that will be very easy to use with ROS 2 because there isn't a portable way to do it that of which I am aware.
peer-to-peer communication
After connecting discovery, you still need individual nodes to be able to communicate with each other.
In ROS 1 this is very hard because nodes let the OS pick ports randomly, so you don't know how to NAT or open your firewall to let them talk.
In ROS 2, the ports that are used are deterministic according to an algorithm, for example see:
https://eprosima-fast-rtps.readthedocs.io/en/latest/pubsub.html#id4
So you could open the right range of ports for peer-to-peer in ROS 2 if you wanted.
summary
So in summary, it's possible to do discovery over the internet with ROS 1, but not realistic to do discovery with ROS 2 over the internet. For peer-to-peer, it's impossible to predict the ports ROS 1 will use, but you can predict and therefore open up ports for ROS 2.
But for both ROS 1 and ROS 2, I wouldn't suggest exposing either publicly to the internet for security reasons.
So in conclusion, I would recommend using VPN for either ROS 1 or ROS 2, for both simplicity and security.
Originally posted by William with karma: 17335 on 2018-03-27
This answer was ACCEPTED on the original site
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Original comments
Comment by gvdhoorn on 2018-03-28:
re: VPN: you could take a look at tinc. It's a relatively easy to setup peer-to-peer VPN, works on just about any platform and deals with NAT and other weird networking setups transparently.
Comment by cbquick on 2018-03-28:
Thank you both!
@William
Would it be possible, with the public IP address to the Internet based nodes, to use the fast RTPS 'Advanced Configuration' options for network configuration, listening locators, and sending locators to specify nodes on different networks and get ROS2 communication working?
Comment by William on 2018-03-28:
@cbquick, yes, though it depends on whether or not you can do this without changing the code itself (not sure off hand). It might be something the Fast-RTPS community could answer better than me.
Comment by William on 2018-03-28:
We don't expose those options through our API, but if you know you're using Fast-RTPS you can get the Fast-RTPS objects directly from our API like this: https://github.com/ros2/demos/blob/master/demo_nodes_cpp_native/src/talker.cpp
Comment by shoemakerlevy9 on 2018-05-21:
Does ROS2 still use the ros_master_uri environment variable?
Comment by Dirk Thomas on 2018-05-21:
No, ROS 2 doesn't use any master and therefore also not that environment variable.
