[SOLVED] eventsource.onmessage is not invoked

eventsource.onmessage is not invoked - flask application

I have been developing a flask application and where trying to implement SSE. Check my code below:

index.py

@app.route('/stream', methods=['GET'])
@cross_origin()
def stream():
    def listenstream():
        print("listening")
        displaytext =  { 'requestdata':  'Sampledata', 'responsedata' : 'Sample Data'}
        displaytext=json.dumps(displaytext)
        yield 'event: message\n'
        yield 'data : '+displaytext+'\n\n'
        time.sleep(1.5)

    return Response(response=listenstream(),status=200,mimetype="text/plain",content_type='text/event-stream')

custom.js

var eventSource = new EventSource("/stream");

eventSource.onmessage = function (e) {
   console.log("Onmessage"+e)
}


eventSource.onerror = function (e) {
   console.log("Onerror"+JSON.stringify(e))
}

eventSource.onopen = function (e) {
   console.log("Onopen"+JSON.stringify(e))
}

Here eventSource.onerror => {"isTrusted":true} ,eventSource.onopen => {"isTrusted":true} but eventSource.onmessage is not being invoked. I tried addEventListener in js file:

var eventSource = new EventSource("/stream");
eventSource.addEventListener('message', (e) => {

console.log("Received update")
})

If I render to the link 'http://localhost:5000/stream', it gives :

event: message

data : {"requestdata": "Sampledata", "responsedata": "Sampledata"}

But I need the data on the link 'http://localhost:5000'. Is this the correct way of doing it?

Help will be appreciated :)

Solution

Following updation resolved the issue for me :

index.py

     yield "event: {0}\ndata: {1}\n\n".format("listen",displaytext)

return Response(listenstream(), mimetype="text/event-stream")

custom.js

var eventSource = new EventSource("/stream");
eventSource.addEventListener('listen', function(e){ 

//Code here
},false);