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Comment by fweespeech | Hacker News Reader

SSE is awesome...except for the fact that IE has 0% support and is too popular to ignore.

It is a very pretty demo tho, well done :)

SSE is easy to shim! We use: https://github.com/Yaffle/EventSource/

Sadly these shims require a per-client queue to ensure message delivery, as events will otherwise be lost during reconnections.

I'm not sure I'm following you. How does this differ from native EventSource?

EventSource sends all events over a single connection which it keeps open indefinitely. This shim receives a single event and then reconnects. In that window there is a period where there will be no connection to send events over, so they will be lost without a queue.

Edit: actually this looks to be a lot more sophisticated than the other shims i havr looked at and does indeed behave more like eventsource. Good job!

Ah, you're suggesting that the shims use long-polling. I don't think that's the case though. If I understand the library correctly, it really is keeping a connection open, so it's really very similar to the way EventSource works.

Addition: Verified. It doesn't disconnect between events (not long-polling).

Really you should have a queue anyway to account for those on less reliable connections (mobile, satellite, comcast)

EventSource natively supports this via the "Last-Event-ID" header (and can also be used by a shim to ensure it gets messages it missed). And in the case of a room style app you probably already have a room history that can be used to provide this data.

That looks like a very high quality shim, so that is good.

However, why would I want to use a shim over websockets?

http://caniuse.com/#feat=websockets

I'm not sure how much of this still holds true, but here's a few reasons you might want to stick to HTTP: https://speakerdeck.com/3rdeden/websuckets

tl;dr websockets can fail in strange ways on mobile and when passed through proxies and corporate firewalls

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