Re: [mosquitto-dev] Moving away from libwebsockets

[Roger Light <roger@xxxxxxxxxx>]

On Wed, 3 Feb 2021 at 15:46, Wiebe Cazemier <wiebe@xxxxxxxxxxxx> wrote:
>
> > I am currently looking at using the picohttpparser and wslay libraries
> to provide websockets support.
>
> Just for brainstorming: do websockets really need much special? How wild is it to split input stream on newlines and wait for the upgrade header and then generate/parse websocket frames? There would have to be some protection, like not allowing more than x bytes before the upgrade and such, but perhaps it's an option? It saves having dependencies.

Sure, there's not a huge amount to it. There are some oddities with
wslay that I'm not entirely happy with that may well make it worth
implementing ourselves. The http header part though - I'm not sure
it's worth the effort. picohttpparser is about 600 lines, it's not
exactly a big dependency. As it's not packaged anywhere, I'd
anticipate bundling it in the tar. wslay on the other hand is quite
widely available.

The change to use picohttpparser and wslay wasn't a lot of effort. It
lays the groundwork for moving to our own implementation if we want -
it integrates much better than lws. Importantly though, it's available
now. The default lws settings now disable their external poll support,
and we rely on that working properly in 2.0. That means that
websockets support for 2.0 won't work on the Debian lws packages for
example: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=977637
We've always used the external poll support, but in a way that meant
it wasn't crucial if it was disabled.

tldr: I'd be happy to entertain our own websockets (but probably not
http parser) implementation, but wslay gives a quick win for now for
most situations.

Regards,

Roger