[layer8]

What is particular about IE7? According to https://caniuse.com/eventsource, SSE is unsupported through IE11.

[bullen]

You don't need to use Event-Source to use SSE, look at how I implemented it here:

https://github.com/tinspin/fuse/blob/master/res/play.html#L1...

The XHR ready state 3 was wrongly implemented in IE7, they fixed it in IE8.