I wonder though, doesn't SSE technically violate a lot of HTTP's assumptions? From the point of view of a HTTP middlebox, a SSE response would basically be a single endless entity, transmitted at a very low bandwidth. I'm no expert at real-world deployment of SSE, but that they sounds to me like it could break a lot of proxies that don't have special handling for SSE. (Or at least cause unnecessary resource consumption for those proxies)

Also I wonder why there are not more websocket-based APIs. WS has the same widespread support and ready-made debug tools as HTTP and seemed to be designed exactly for push or non request/response use cases. So, out of couriosity, why would SSE be preferred over WS?

Streamdata.io (linked in a different post) has blogged [1] about why they chose SSE instead of WS. Additionally, WS drops you down to something very similar to raw TCP, so you have to bring your own application-level message framing, while SSE comes with its own minimalistic format. From a middle box's perspective, SSE isn't that different from streaming video or long polling, although the SSE recommendation [2] does have a line about older proxies:

"Legacy proxy servers are known to, in certain cases, drop HTTP connections after a short timeout. To protect against such proxy servers, authors can include a comment line (one starting with a ':' character) every 15 seconds or so."

[1] http://streamdata.io/blog/push-sse-vs-websockets/

[2] https://html.spec.whatwg.org/multipage/comms.html#authoring-...

As far as I know, two of the few things WS does on top of TCP are in fact: making endpoints URL-addressable - and providing message framing. You can even have text-only frames with a well-defined encoding.

In any way though, thanks for the links. I haven't given them a deep read yet but will definitely do so soon.

I wonder though, doesn't SSE technically violate a lot of HTTP's assumptions? From the point of view of a HTTP middlebox, a SSE response would basically be a single endless entity, transmitted at a very low bandwidth. I'm no expert at real-world deployment of SSE, but that they sounds to me like it could break a lot of proxies that don't have special handling for SSE. (Or at least cause unnecessary resource consumption for those proxies)

Also I wonder why there are not more websocket-based APIs. WS has the same widespread support and ready-made debug tools as HTTP and seemed to be designed exactly for push or non request/response use cases. So, out of couriosity, why would SSE be prepared over WS?

It looks like you accidentally duplicated your comment when you changed "prepared" to "preferred".

I'm sorry. That was my attempt at "editing" the post after the noprocrast mode kicked in - before an unintelligible post would sit there for ~3 hours...

If any mods could delete this, I'd be grateful.