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October 1, 2019 14:43
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server side events using flask
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| # ref: https://stackoverflow.com/questions/12232304/how-to-implement-server-push-in-flask-framework | |
| import datetime | |
| import time | |
| import json | |
| from flask import Flask, Response | |
| app = Flask(__name__) | |
| def event_stream(): | |
| while True: | |
| yield "data: {}\n\n".format(str(datetime.datetime.now())) | |
| time.sleep(1) | |
| def event_stream2(): | |
| while True: | |
| n = datetime.datetime.now() | |
| yield "data: {}\n\n".format(json.dumps({ | |
| "datetime": str(n), | |
| "timestamp": n.timestamp() | |
| })) | |
| time.sleep(1) | |
| @app.route('/') | |
| def root(): | |
| return 'Hello World from Python Flask!' | |
| @app.route('/test') | |
| def test(): | |
| return """ | |
| <html> | |
| <body> | |
| <h3>Evensource based notifications - Test 1</h3> | |
| <p>check the console logs!</p> | |
| <ul></ul> | |
| <script type="text/javascript"> | |
| var source = new EventSource('/stream'); | |
| var eventList = document.querySelector('ul'); | |
| source.onmessage = function (e) { | |
| console.log(e); | |
| var newElement = document.createElement("li"); | |
| newElement.textContent = "received message: " + e.data; | |
| eventList.appendChild(newElement); | |
| }; | |
| source.onopen = function (e) { | |
| console.log("opening eventsource connection"); | |
| console.log(e); | |
| var newElement = document.createElement("li"); | |
| newElement.textContent = "opening eventsource connection"; | |
| eventList.appendChild(newElement); | |
| }; | |
| </script> | |
| </body> | |
| </html> | |
| """ | |
| @app.route('/test2') | |
| def test2(): | |
| return """ | |
| <html> | |
| <body> | |
| <h3>Evensource based notifications - Test 2</h3> | |
| <p>check the console logs!</p> | |
| <ul></ul> | |
| <script type="text/javascript"> | |
| var source = new EventSource('/stream2'); | |
| var eventList = document.querySelector('ul'); | |
| source.onmessage = function (e) { | |
| console.log(e); | |
| data = JSON.parse(e.data); | |
| var newElement = document.createElement("li"); | |
| newElement.textContent = "received message: " + data.timestamp; | |
| eventList.appendChild(newElement); | |
| }; | |
| source.onopen = function (e) { | |
| console.log("opening eventsource connection"); | |
| console.log(e); | |
| var newElement = document.createElement("li"); | |
| newElement.textContent = "opening eventsource connection"; | |
| eventList.appendChild(newElement); | |
| }; | |
| </script> | |
| </body> | |
| </html> | |
| """ | |
| @app.route('/stream') | |
| def stream(): | |
| return Response(event_stream(), mimetype="text/event-stream") | |
| @app.route('/stream2') | |
| def stream2(): | |
| return Response(event_stream2(), mimetype="text/event-stream") | |
| if __name__ == '__main__': | |
| app.debug = True | |
| # app.run(port=8085, threaded=True) | |
| app.run(port=8085) # threaded is True by default since flask version 1.0 |
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/test -> simple string data
/test2 -> sends json string data, and parse as json in javascript (see usage in line 77: JSON.parse)