This app is part of a small whitelist of apps that can make this type of connection. It's a temporary solution though. The Chrome team is working on ways to make the functionality more widely available.
Just got through scouring the pepper 19 docs for any mention for how this was done. Exciting to see this kind of functionality enabled, but apprehensive about chrome apps developing into an android style permission nightmare. Perhaps if the user always had the ability to arbitrarily revoke permissions and block them by default.
I'd been checking every few months for the last several years to see if sockets were available in NaCL, for this exact killer app (along with a vnc/rdesktop client)
Sad that it had to be done with an internal whitelist, but I'm mostly just happy that it exists for me to use even if I didn't get to write it!