[jcranmer]

> Firefox OS had TCP[0] and UDP[1] sockets as Web APIs. They were quite pleasant to use as a developer and the only way to create a real mail client (needs TCP to implement POP, IMAP, SMTP in JS).

The biggest problem with Firefox OS's TCP standard is that it used an event-driven model, which is somewhat at odds with more current promise-based thinking. The more natural version is to use something based on WHATWG Streams, but that spec has been stuck in vaporware-land for years.

> I wish more Firefox OS APIs had become web standards. They would allow for some very powerful PWAs.

The TCP specification actually was undergoing standardization (reformatted to use the streams API): https://www.w3.org/TR/tcp-udp-sockets/ . The problem was the working group ended up closing down, and since the specification wasn't suitable for use on webpages, it ended up with nobody to host it.