view topic remotely (both robot and remote PC behind a router)

edit

I'm following this link to create a multi machine setup. http://wiki.ros.org/ROS/Tutorials/Mul...

But this only seem work for machines in the same sub-network. I'm trying to do that across different networks.

Info: Robot's sub-net adress: 192.168.1.100. Robot is behind a wifi router / modem. The modem's public address is: 11.22.33.44. remote PC's sub-net address: 192.168.1.150. Remote PC is also behind a wifi router /modem. The modem's public address: 55.66.77.88.

Is it possible to establish ROS connection between these two PCs? Thank you.

Would VPN help?