title: How do server-side events keep the connection open despite using HTTP?
body: <p>I am confused at how SSE, despite using HTTP, is able to maintain the connection.</p>
  <p>When I look at Web sockets, my understanding is that the most that HTTP is used is only for establishing the TCP connection and asking to upgrade to WS protocol. After that, the client and server both use the WS protocol which is why the connection can be persisted.</p>
  <p>With SSE, there is no special protocol, it's just HTTP. Don't browsers have an HTTP TTL? How is the connection persisted beyond the TTL then?</p>
  <p>Other HTTP polling mechanisms still suffer from timeout. SSE isn't a polling mechanism, but it still uses HTTP.</p>