server-push

There has always been problem for pushing data from server side to client side. Here is the solution using HTML 5 web sockets and python. This is plug and play kind of websocket server which can push data to the client side(vice-versa). Prerequisite: python tornado webserver. Install using following command in the cmd prompt pip install tornado OR easy_install tornado

For detail see server-push.pdf

Uses

1. Pushing data from server side
2. Getting data from client side
3. Making chat application

server-push

There has always been problem for pushing data from server side to client side. Here is the solution using web sockets and tornado webserver(python).

This is plug and play kind of websocket server which can push data to the client side and vice-versa.

Prerequisite : tornado webserver. Install using following command in the cmd line

pip install tornado OR easy_install tornado

Step 1 : Run server.py on server(Now server is ready for conversation using websockets) using following cmd

python server.py

Step 2 : Copy and paste the below code on client’s HTML page

        $(document).ready(function () {

            var ws;
            var host = '192.168.1.1'; //server IP
            var port = '8888'; //server port
            var uri = 'ws'; //websocket uri
            ws = new WebSocket("ws://" + host + ":" + port + uri); //create web socket object

            //Called when connection is established with server
            ws.onopen = function (evt) {
                alert("Connection open");
            };

            //Called when message is sent from server
            ws.onmessage = function (evt) {
                alert("message received: " + evt.data)
            };

            //Called when connection is closed from server
            ws.onclose = function (evt) {
                alert("Connection close");
            };
        });

Step 3 : Understanding server side code(server.py)

from tornado import httpserver
import tornado.websocket
import tornado.ioloop
import tornado.web
clients = []
userid = 0
class WSHandler(tornado.websocket.WebSocketHandler):
#Called when attempt is made for connection from client
def open(self):
    obj = SessionManagement()
    obj.createsession(self)#storing web socket object for further communication with client
 
#Called when client sends message  
def on_message(self, message):
    print 'message received %s' % userid

#Called when user refreshes or closes the page
def on_close(self):
    obj = SessionManagement()
    obj.deletesession(self)#deleting web socket object
    print 'connection closed'

class SessionManagement():
#Create session and stores into array
def createsession(self, obj):
userid = obj.get_argument("userid")
componentid = obj.get_argument("compid")
clients.append({"wsobj":obj, "userid":userid, "compid":componentid})
for w in clients:
print w
#Delete session from array when client refreshes the page or closes the page

def deletesession(self, obj):
for temp in clients:
if cmp(obj, temp['wsobj']):
clients.remove(temp)
for w in clients:
print w
class PushToUser(tornado.web.RequestHandler):
def get(self):
userid = self.get_argument('userid')
compid = self.get_argument('compid')
message = self.get_argument('message')
for temp in clients:
if (temp['userid'] == userid and temp['compid'] == compid):
temp['wsobj'].write_message(message)
class PushToAll(tornado.web.RequestHandler):
def get(self):
message=self.get_argument('message')
for temp in clients:
temp['wsobj'].write_message(message)
application = tornado.web.Application([
(r'/ws', WSHandler),
(r'/push', PushToUser), #Ex. /push?userid=123&compid=123&message=hello
(r'/pushtoall', PushToAll), #Ex. /pushtoall?message="hello"
])
if name == "main":
http_server = tornado.httpserver.HTTPServer(application)
http_server.listen(8888)
tornado.ioloop.IOLoop.instance().start()

Step 4: Sending message to client using REST

- Push message to specific user

- Push message to all users

Done!!!!!