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POWebSocket Server sending messages periodically in python
 

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    <p>I have a tornado web server in python:</p> <pre><code>import tornado.httpserver import tornado.websocket import tornado.ioloop from tornado.ioloop import IOLoop import tornado.web import time import threading import sys from datetime import datetime from datetime import timedelta def sample(): print 'hiiiii' threading.Timer(10, sample).start() class WSHandler(tornado.websocket.WebSocketHandler): def open(self): print 'new connection' def on_message(self, message): self.write_message(message) self.msg('hellooooooo') print message def msg(self,message): self.write_message(message) threading.Timer(10, self.msg('in timer')).start() print 'in msg'+message def on_close(self): print 'connection closed' application = tornado.web.Application([ (r'/', WSHandler), ]) if __name__ == "__main__": http_server = tornado.httpserver.HTTPServer(application) http_server.listen(8888) interval_ms=120 main_loop=tornado.ioloop.IOLoop.instance() main_loop.start() </code></pre> <p>And the client is </p> <pre><code>&lt;html&gt; &lt;head&gt; &lt;script&gt; function fun(){ alert("in fun()"); var val=document.getElementById("txt"); var ws = new WebSocket("ws://localhost:8888"); ws.onopen = function(evt) { alert("Connection open ..."); ws.send(val.value); }; ws.onmessage = function(evt) { alert("from server: "+evt.data); } ws.onclose = function(evt) { alert("Connection closed."); } } &lt;/script&gt; &lt;/head&gt; &lt;body bgcolor="#FFFFFF"&gt; &lt;input type="text" id="txt" /&gt; &lt;button onClick="fun()"&gt;click&lt;/button&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>I want to get the message periodically to the client. But when I try this I get this error: <code>RunTimeError :Maximum Recursion Depth Exceeded.</code> Please help me solve this issue. Also, how do we know what are the clients connected to the server?</p>
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    1. CODon't use `threading`. Have a look at `IOLoop.add_timeout` and especially `tornado.ioloop.PeriodicCallback`. Don't forget to remove the callback when the connection is closed.
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    2. COHi Thijs van Dien,Thanks but how to remove the callback?
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    3. COI tried this def open(self): print 'new connection' main_loop=tornado.ioloop.IOLoop.instance() scheduler=tornado.ioloop.PeriodicCallback(self.msg('testing'),interval_ms,io_loop=main_loop) scheduler.start() main_loop.start() But am getting error : Traceback (most recent call last): File "/Library/Python/2.7/site-packages/tornado/ioloop.py", line 814, in _run self.callback() TypeError: 'NoneType' object is not callable ERROR:tornado.application:Error in periodic callback
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