J. Daniel J. Daniel - 4 months ago 32
Python Question

Tornado send message on event

Im creating a program in Python that reads a stream of data on an unknown interval. This program also sends this data through websockets.
The program is the server and it sends the received data to the clients.

This is the code of the server now:

class WebSocketHandler(tornado.websocket.WebSocketHandler):
def initialize(self):
print 'Websocket opened'

def open(self):
print 'New connection'
self.write_message('Test from server')

def on_close(self):
print 'Connection closed'

def test(self):

def make_app():
return tornado.web.Application([
(r'/ws', WebSocketHandler),

if __name__ == '__main__':
application = make_app()

http_server = tornado.httpserver.HTTPServer(application)

But I want to be able to use
in this loop:

def read_function():
while True:
time.sleep(10) # a while loop to simulate the reading
print 'read serial'
str = 'string to send'
# send message here to the clients

How am I supposed to do this?


Use connections = set() outside the WebsocketHandler and add every client on opening a connection with connections.add(self). Do not forget to remove them on closing with connections.remove(self).

Now, you are able to access write_message out of the websocket thread through: [client.write_message('#your_message') for client in connections]