CODEWITHSUNDEEP
pythonlong-pollingserver-sent-events
Anum Sheraz
Anum Sheraz

Reputation: 2625

Issues in creating web app with SSE + long polling

i am new in web development. i am creating a web app for my home automation project, in which i need bi-directional communication. any theft-security alert from home will be send to client from server or if client want to control the main gate, he'll sent a POST request to server. I am still confused what thing to use, SSE or Web sockets. my question is, is it possible to develop an app that uses both, SSE as well as handles traditional (long-polling) HTTP requests from client (GET/POST) ? i have tested each of them individually and they work fine but i am unable to make them work together. i am using python BaseHTTPServer. Or at last, do i have to move to WebSocket? Any suggestion will be highly appreciated. my code here is;

import time
import BaseHTTPServer
from BaseHTTPServer import HTTPServer, BaseHTTPRequestHandler
from SocketServer import ThreadingMixIn

import os
import requests
import threading
from threading import Thread
from chk_connection import is_connected
import socket


HOST_NAME = socket.gethostbyname(socket.gethostname())
PORT_NUMBER = 8040 # Maybe set this to 9000.
ajax_count=0
ajax_count_str=""
switch=0
IP_Update_time=2 
keep_alive=0
connected=False


###############################

##############

my_dir = os.getcwd()


class MyHandler(BaseHTTPServer.BaseHTTPRequestHandler):
 def do_HEAD(s):
    s.send_response(200)
    s.send_header("Content-type", "text/html")
    s.end_headers()



def do_POST(s):

    global keep_alive

    """Respond to a POST request."""
    s.send_response(200)
    s.send_header('Access-Control-Allow-Origin', '*')
    s.send_header("Content-type", "text/html")
    s.end_headers()
    HTTP_request=s.requestline

    if HTTP_request.find('keep_alive')>-1:
             keep_alive += 1
             keep_alive_str = str(keep_alive)
             s.wfile.write(keep_alive_str)  #sending ajax calls for keep alive 




def do_GET(s):
    global ajax_count
    global my_dir
    global switch
    global ajax_count_str
    global keep_alive
    #print 'got Get',
    """Respond to a GET request."""
    s.send_response(200)
    #s.send_header('Access-Control-Allow-Origin', '*')
    s.send_header('content-type', 'text/html')
    s.end_headers()
    print s.headers
    HTTP_request=s.requestline
    index_1=HTTP_request.index("GET /")
    index_2=HTTP_request.index(" HTTP/1.1")
    file_name=HTTP_request[index_1+5:index_2]
    #print 'file_name:',file_name
    #print 'HTTP_request:',HTTP_request 
    #if len(file_name)>0:

    #if HTTP_request.find('L2ON')>-1:
    #        print 'sending SSE'
    #        s.wfile.write('event::'.format(time.time()))




    elif HTTP_request.find('GET / HTTP/1.1')>-1: 
        print 'send main'
        file1=open('Index.html','r')
        file_read=file1.read()
        s.wfile.write(file_read)


    elif file_name.find("/")==-1:
           for root, dirs, files in os.walk(my_dir):
               #print 'in for 1' 
               for file in files:
                 #print 'in for'  
                 if HTTP_request.find(file)>-1:
                    file_path=os.path.join(root,file)
                    file1=open(file_path,'r')
                    file_read=file1.read()
                    s.wfile.write(file_read)
                    print 'send',file

    elif file_name.find("/")>-1:
             #print 'get /...'
             slash_indexes=[n for n in xrange(len(file_name)) if file_name.find('/', n)==n]
             length=len(slash_indexes)
             slash=slash_indexes[length-1]
             file_path=file_name[0:slash]
             root_dir=(my_dir + '/' + file_path + '/')
             for root, dirs, files in os.walk(root_dir): 
               for file in files: 
                  if HTTP_request.find(file)>-1:
                    image_path=os.path.join(root,file)
                    image=open(image_path,'r')
                    image_read=image.read()
                    s.wfile.write(image_read)
                    print 'send',file
                  #else:
                    #print 'file not found'


class MyHandler_SSE(BaseHTTPRequestHandler):
 print 'SSE events class'
 def do_GET(self):
    print 'this is SSE'
    self.send_response(200)
    self.send_header('content-type', 'text/event-stream')
    self.end_headers()
    while True:
        print 'SSE sent'
        self.wfile.write('event: message\nid: 1\ndata: {0}\ndata:\n\n'.format(time.time()))
        time.sleep(2)





class chk_connection(threading.Thread):
  """
  # this thread checks weather there is internet connection available ? 
  """
  def __init__(self):
    threading.Thread.__init__(self)

  def run(self):
    global connected
    while 1:
     ########################################################## INSIDE THE            chk_connection import is_connected
    #import socket
    #REMOTE_SERVER = "www.google.com"
    #def is_connected():
    #try:
    #   # see if we can resolve the host name -- tells us if there is
    #   # a DNS listening
    #   host = socket.gethostbyname(REMOTE_SERVER)
        # connect to the host -- tells us if the host is actually
        # reachable
    #   s = socket.create_connection((host, 80), 2)
    #   return True
    #except:
    #   pass
    #return False
     ##########################################################
        connected=is_connected()
        #print 'internet:', connected
        time.sleep(1)


class server_main(threading.Thread):
 """


 """
 def __init__(self):
    threading.Thread.__init__(self)


 def run(self):
    global connected


    #print 'shutdown started'
    server_class = BaseHTTPServer.HTTPServer
    HOST_NAME = socket.gethostbyname(socket.gethostname())
    last_HOST_NAME = HOST_NAME
    httpd = server_class((HOST_NAME, PORT_NUMBER), MyHandler)
    #http_SSE = server_class((HOST_NAME, PORT_NUMBER), MyHandler_SSE)
    print time.asctime(), "Server Starts - %s:%s" % (HOST_NAME, PORT_NUMBER)
    while(1):       
      while is_connected():
        httpd._handle_request_noblock()
        #print 'no block'
        #http_SSE._handle_request_noblock()
      time.sleep(1)  
      HOST_NAME = socket.gethostbyname(socket.gethostname())
      if HOST_NAME != last_HOST_NAME:
          print 'Serving at new host:', HOST_NAME
      httpd = server_class((HOST_NAME, PORT_NUMBER), MyHandler)  


def start():

tx_socket_thread3 = chk_connection()   # this thread checks weather there is internet connection available ?
tx_socket_thread3.start()

tx_socket_thread5 = server_main()
tx_socket_thread5.start()
print 's1:',tx_socket_thread1.is_alive()

if __name__ == '__main__':

 start()

i might need to modify the code in a new manner, but don't know how. What i want is, if any interrupt happens at server side, it pulls data to client, and mean while it also responds to the GET and POST requests from client. Help Plx...

Upvotes: 1

Views: 477

Answers (1)

Mikko Ohtamaa
Mikko Ohtamaa

Reputation: 83758

It is definitely possible to develop a web application which uses a mixture of normal HTTP traffic, server-side events and WebSockets. However, the web server classes in Python standard library are not designed for this purpose, though one can probably make them to work with enough hammering. You should to install a proper web server and use it facilities.

Examples include

Furthermore

Upvotes: 1

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