WebSocket Server sending messages periodically in python

问题

I have a tornado web server in python:

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()

And the client is

<html>
<head>
<script> 

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.");
    }
}

</script>

</head>
<body bgcolor="#FFFFFF">
    <input type="text" id="txt" />
    <button onClick="fun()">click</button>
</body>
</html>

I want to get the message periodically to the client. But when I try this I get this error: RunTimeError :Maximum Recursion Depth Exceeded. Please help me solve this issue. Also, how do we know what are the clients connected to the server?

回答1:

Here's a minimal example using the PeriodicCallback.

import tornado.httpserver
import tornado.websocket
import tornado.ioloop
from tornado.ioloop import PeriodicCallback
import tornado.web

class WSHandler(tornado.websocket.WebSocketHandler):
    def open(self):
        self.callback = PeriodicCallback(self.send_hello, 120)
        self.callback.start()

    def send_hello(self):
        self.write_message('hello')

    def on_message(self, message):
        pass

    def on_close(self):
        self.callback.stop()

application = tornado.web.Application([
    (r'/', WSHandler),
])

if __name__ == "__main__":
    http_server = tornado.httpserver.HTTPServer(application)
    http_server.listen(8888)
    tornado.ioloop.IOLoop.instance().start()

回答2:

You are calling the function in stead of starting a timer. Do this:

threading.Timer(10, self.msg, args =('in timer',)).start()

回答3:

could those examples help you

Tornado example

also this too Documentation tornado WS

来源：https://stackoverflow.com/questions/19542333/websocket-server-sending-messages-periodically-in-python

标签

python

websocket

tornado

periodic-task