SSE（服务器发送的事件）断开连接

Question

I'm trying to use SSE (in chrome) for a ticker application. It seems that in every sample I found or wrote the connection is closed every 3-4 seconds. Even when running the example at : http://www.w3schools.com/html5/tryit.asp?filename=tryhtml5_sse

you can see that an update arrives every 3-4 seconds. This is not due to the server implementation ("demo_sse.php" in this example), but due to a reconnect which occurs every 3-4 seconds.

If I add the following to the above example:

source.onerror=function(event)
{
  document.getElementById("result").innerHTML+=source.readyState+ "<br />";
};

you can clearly see that the readyState is 0, meaning : "The connection has not yet been established, or it was closed and the user agent is reconnecting." (taken from the official EventSorce API doc).

I wrote a script for the server side by myself as well, Here is the code (using python bottle web framework).

@route('/events')
def positions():  
    response.content_type = 'text/event-stream'
    response.set_header('Cache-Control', 'no-cache')
    now = datetime.datetime.now().time().replace(microsecond=0)
    return  "data: %s\n\n"%now

And i get the same thing. Reconnecting every 3-4 seconds.

So what I'm interested is in how the connection is kept through the session.

Thanks for your help, Omer.

Answer 1

Make sure bottle is not setting the Content-Length header for you. This line looks suspicious to me.

Returning an iterator, as suggested in this issue for bottle , will probably do what you want.

@route('/events')
def positions():
  yield 'START'
  while stream_alive:
      some_event.wait()
      yield some_data()
  yield 'END'

Answer 2

AFAIK, SSE is defined to work through those reconnections. You may trick them content-length hackery... Like establishing content-length 0 in your headers.