communicating with remote autonomous robots

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I have multiple autonomous robots operating in remote locations, each of which have their own ROS master. They are just regular network clients in their LANs, with no port forwarding or dedicated WAN IPs.

I'm looking for a way of communicating with each of the autonomous robots to allow for send commands and to receive data through the Internet. I have my general network setup and an idea about how to use vpn+multimaster as a solution illustrated below.

What are some solutions to this kind of setup?

Is there a way for the remote ROS masters to act as websocket clients instead of servers and connect to a websocket server in the remote base station to establish communication? roslibjs seems to work the other way around, with a websocket server on each master. This would require port forwarding on each robot I think, which is something I want to avoid.

• http://wiki.ros.org/multimaster_fkie
• http://robotwebtools.org/

Thanks

General situation

OpenVPN with multimaster idea