If you want to use the protocol within a browser, there is no standard (included by default in the browser) UDP socket interface accessible from js. Nice to use JSON but I'm still wondering how they could use UDP from the Browser? using "faked" DNS queries to generate UDP traffic?

There's a reason most of the world uses TCP.. even for things that sound ideal for UDP.

When you've got a hammer...

TCP isn't ideal for everything. Ad-hoc networking and broadcast streaming being just two.

There's a reason why UDP was invented.

JXTA handles this by specifying neither. Instead they have a "pipe" abstraction. Once peers discover each other they can open a pipe that may, depending upon the network conditions, be a fast TCP implementation (when a direct connection is possible) or a slower, but usable pipe built on HTTP with polling (for being able to traverse firewalls).

Exactly, it's the only option left in order to let apps talk directly across the unwieldily myriad of network configurations (NATs).