gistfile1.py

from twisted.web.resource import Resource
from twisted.web import server
from flask import Flask, render_template_string
from twisted.web.wsgi import WSGIResource
from twisted.internet import reactor
from twisted.internet.task import LoopingCall
import json


INDEX_TEMPLATE = """
<title>Hello world!</title>
<script>
var es = new EventSource("/es");
var messageDump;

es.onerror = function(evt){
    mes("Closed!");
};

es.onopen = function(evt){
    mes("Open!");
}

es.onmessage = function(evt){
    var text = JSON.parse(evt.data).data;
    mes(text);
}

function mes(text){
    var li = document.createElement("li");
    li.innerText = text;
    messageDump.insertBefore(li, messageDump.firstChild);
};

document.addEventListener('DOMContentLoaded', function(){
    messageDump = document.getElementById("messages");
}, false);

</script>
<ul id=messages>
</ul>
"""

# the twisted ES part, it just keeps the incoming requests as self.clients

class EventSource(Resource):
    clients = []

    def send_event(self, request, event, data):
        message = json.dumps({"event": event, "data": data})
        request.write('data: %s\n\n' % message)

    def send_to_all(self, event, data):
        for client in self.clients:
            self.send_event(client, event, data)

    def render_GET(self, request):
        request.setResponseCode(200)
        request.setHeader('Content-Type', 'text/event-stream')

        request.notifyFinish().addBoth(self.close_es_request, request=request)

        self.clients.append(request)
        self.send_event(request, "hello", "Hello! There are %d clients connected" % len(self.clients))

        return server.NOT_DONE_YET

    def send_old_events(self, request, last_id, count=10):
        for num, (current_id, event, data) in enumerate(self._sent):
            if num > count or current_id <= last_id:
                break
            self.send_event(request, event, data)

    def close_es_request(self, error=None, request=None):
        self.clients.remove(request)

# let's just instantiate one global ES resource
es_resource = EventSource() 

# send a heartbeat to all ES clients once in a while just to see if it works
heartbeat = LoopingCall(es_resource.send_to_all, event="hearbeat", data="Heartbeat!")
heartbeat.start(5)


# flask app

app = Flask(__name__)

@app.route('/')
def index():
    return render_template_string(INDEX_TEMPLATE)



# serving stuff, boilerplate mostly

class Root(Resource):
    def getChild(self, path, request):
        request.postpath.insert(0, request.prepath.pop(0))
        return flaskAppResource

flaskAppResource = WSGIResource(reactor, reactor.getThreadPool(), app.wsgi_app)
root = Root() # /<anything> -> flask app, with the exception of...

root.putChild("es", es_resource) # /es -> EventSource()

site = server.Site(root)
reactor.listenTCP(5000, site)
reactor.run()