In case anyone else wants to do the same, this is the simplest example I could boil things down to based on the example by reptilicus...
Instructions
- Set the code below laid out in the structure mentioned below.
- Install the Python modules listed below
- Run the server
- Run the data source
- Open a web browser and navigate to
http://localhost:25000/
If everything worked you should see a very basic page along these lines:
Python / Modules
These were the versions my test implementation used. Others may work too.
- Python v3.5.2
- Pyzmq v15.2.0
- gevent v1.2.0
- karellen-geventws v1.0.1 (required over gevent-websocket for Python 3 support)
- Flask v0.10.1
- Flask-Sockets v0.2.1
You also need a copy of Reconnecting Websocket, available here.
Code layout
\ZmqFlaskForwarder
\static
\js
application.js
reconnecting-websocket.min.js
\templates
index.html
data_source.py
server.py
Server App (server.py)
import zmq.green as zmq
import json
import gevent
from flask_sockets import Sockets
from flask import Flask, render_template
import logging
from gevent import monkey
monkey.patch_all()
app = Flask(__name__)
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
sockets = Sockets(app)
context = zmq.Context()
ZMQ_LISTENING_PORT = 12000
@app.route('/')
def index():
logger.info('Rendering index page')
return render_template('index.html')
@sockets.route('/zeromq')
def send_data(ws):
logger.info('Got a websocket connection, sending up data from zmq')
socket = context.socket(zmq.SUB)
socket.connect('tcp://localhost:{PORT}'.format(PORT=ZMQ_LISTENING_PORT))
socket.setsockopt_string(zmq.SUBSCRIBE, "")
poller = zmq.Poller()
poller.register(socket, zmq.POLLIN)
gevent.sleep()
received = 0
while True:
received += 1
# socks = dict(poller.poll())
# if socket in socks and socks[socket] == zmq.POLLIN:
data = socket.recv_json()
logger.info(str(received)+str(data))
ws.send(json.dumps(data))
gevent.sleep()
if __name__ == '__main__':
logger.info('Launching web server')
from gevent import pywsgi
from geventwebsocket.handler import WebSocketHandler
server = pywsgi.WSGIServer(('', 25000), app, handler_class=WebSocketHandler)
logger.info('Starting serving')
server.serve_forever()
Data Source (data_source.py)
import zmq
import random
import sys
import time
import json
port = "12000"
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://*:%s" % port)
while True:
first_data_element = random.randrange(2,20)
second_data_element = random.randrange(0,360)
message = json.dumps({'First Data':first_data_element, 'Second Data':second_data_element})
print(message)
socket.send_string(message)
time.sleep(0.5)
Client JavaScript (application.js)
ws = new ReconnectingWebSocket("ws://" + location.host + '/zeromq')
ws.onmessage = function(message) {
payload = JSON.parse(message.data);
$('#latest_data').html('<h2> Data: ' + message.data + '</h2>');
};
Template (index.html)
<!DOCTYPE html>
<html>
<head>
<title>Python Websockets ZeroMQ demo</title>
</head>
<body>
<div class="container">
<h2> Simple ZeroMQ data streaming via web sockets! </h2>
<div id="latest_data"></div>
</div>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<script type="text/javascript" src="static/js/reconnecting-websocket.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.6/d3.min.js"></script>
<script type="text/javascript" src="static/js/application.js"></script>
</body>
</html>
