I am trying to build a websocket server to run on the Raspberry Pi. The websocket server has to push periodic realtime update to a browser. Here is a sample code that I am planning to use. The example code here sends the current time instead of sensor data.
Most of the code is built form an example. However, what I need feedback on is
- The way stpoll is coded (sensor status poll)
- The global variable that passes the message to terminate the thread. I don't like it. Is there a better way to terminate a task that runs forever?
- The way the time (sensor data) is broadcasted to all connected clients. (another global variable)
I had to code this without much documentation.
# -*- coding: utf-8 -*-
import argparse
import random
import os
import time
import threading
import signal
import sys
import cherrypy
from ws4py.server.cherrypyserver import WebSocketPlugin, WebSocketTool
from ws4py.websocket import WebSocket
from ws4py.messaging import TextMessage
class ChatWebSocketHandler(WebSocket):
def received_message(self, m):
cherrypy.engine.publish('websocket-broadcast', m)
def closed(self, code, reason="A client left the room without a proper explanation."):
cherrypy.engine.publish('websocket-broadcast', TextMessage(reason))
class Root(object):
def __init__(self, host, port, ssl=False):
self.host = host
self.port = port
self.scheme = 'wss' if ssl else 'ws'
@cherrypy.expose
def index(self):
return """<html>
<head>
<script type='application/javascript' src='https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js'></script>
<script type='application/javascript'>
$(document).ready(function() {
websocket = '%(scheme)s://%(host)s:%(port)s/ws';
if (window.WebSocket) {
ws = new WebSocket(websocket);
}
else if (window.MozWebSocket) {
ws = MozWebSocket(websocket);
}
else {
console.log('WebSocket Not Supported');
return;
}
window.onbeforeunload = function(e) {
$('#chat').val($('#chat').val() + 'Bye bye...\\n');
ws.close(1000, '%(username)s left the room');
if(!e) e = window.event;
e.stopPropagation();
e.preventDefault();
};
ws.onmessage = function (evt) {
$('#chat').val($('#chat').val() + evt.data + '\\n');
};
ws.onopen = function() {
ws.send("%(username)s entered the room");
};
ws.onclose = function(evt) {
$('#chat').val($('#chat').val() + 'Connection closed by server: ' + evt.code + ' \"' + evt.reason + '\"\\n');
};
$('#send').click(function() {
console.log($('#message').val());
ws.send('%(username)s: ' + $('#message').val());
$('#message').val("");
return false;
});
});
</script>
</head>
<body>
<form action='#' id='chatform' method='get'>
<textarea id='chat' cols='35' rows='10'></textarea>
<br />
<label for='message'>%(username)s: </label><input type='text' id='message' />
<input id='send' type='submit' value='Send' />
</form>
</body>
</html>
""" % {'username': "User%d" % random.randint(0, 100), 'host': self.host, 'port': self.port, 'scheme': self.scheme}
@cherrypy.expose
def ws(self):
cherrypy.log("Handler created: %s" % repr(cherrypy.request.ws_handler))
def stpoll(arg):
global pollStatus
while pollStatus:
tm=time.localtime();
print tm.tm_sec
if 'WebSocket' in globals():
print "WS !"
cherrypy.engine.publish('websocket-broadcast', '%s ' %tm)
time.sleep(2)
print "exitting therad"
def signal_handler(signal, frame):
global pollStatus
pollStatus=False
cherrypy.engine.stop()
cherrypy.engine.exit()
print('You pressed Ctrl+C!')
if __name__ == '__main__':
import logging
from ws4py import configure_logger
configure_logger(level=logging.DEBUG)
signal.signal(signal.SIGINT, signal_handler)
pollStatus=True
thread = threading.Thread(target = stpoll, args = (10, ))
thread.daemon = True
thread.start()
parser = argparse.ArgumentParser(description='Echo CherryPy Server')
parser.add_argument('--host', default='127.0.0.1')
parser.add_argument('-p', '--port', default=9000, type=int)
parser.add_argument('--ssl', action='store_true')
args = parser.parse_args()
cherrypy.config.update({'server.socket_host': args.host,
'server.socket_port': args.port,
'tools.staticdir.root': os.path.abspath(os.path.join(os.path.dirname(__file__), 'static'))})
if args.ssl:
cherrypy.config.update({'server.ssl_certificate': './server.crt',
'server.ssl_private_key': './server.key'})
WebSocketPlugin(cherrypy.engine).subscribe()
cherrypy.tools.websocket = WebSocketTool()
cherrypy.quickstart(Root(args.host, args.port, args.ssl), '', config={
'/ws': {
'tools.websocket.on': True,
'tools.websocket.handler_cls': ChatWebSocketHandler
},
'/js': {
'tools.staticdir.on': True,
'tools.staticdir.dir': 'js'
}
}
)
thread.join()
