[LunaSea]

Not having raw TCP means you can't speak to any existing TCP protocol through a browser. It might not be a useful feature but I think that not taking it into account is an issue because most use cases can't be implemented with WebSockets.

[mrmoka]

Ability to connect to raw TCP or UDP from a browser is a major security hole.

Due to that, WebSockets were created were handshake is handled by browser transparently from developer ensuring port scanning is not possible. As well as to preserver origin-based security model of HTTP. Which we want for WebUDP as well.