sockets - asyncore.dispatcher in python: when are the handle_closed and handle_read executed? -

there 2 files: server.py , client.py, both written of asyncore.dispatcher

server.py

import asyncore, socket  class server(asyncore.dispatcher):     def __init__(self, host, port):         asyncore.dispatcher.__init__(self)         self.create_socket(socket.af_inet, socket.sock_stream)         self.bind(('', port))         self.listen(1)         print "waiting connection..."      def handle_accept(self):         socket, address = self.accept()         print 'connection by', address         socket.send("hello server")      def handle_read(self):         print "reading..."         out_buffer = self.recv(1024)         if not out_buffer:             self.close()         print out_buffer      def handle_closed(self):         print "server: connection closed"         self.close()  s = server('0.0.0.0', 5007) asyncore.loop() 

client.py

import asyncore, socket  class client(asyncore.dispatcher):     def __init__(self, host, port):         asyncore.dispatcher.__init__(self)         self.create_socket(socket.af_inet, socket.sock_stream)         self.connect((host, port))         print "client start..."      def handle_close(self):         print "client: connection closed"         self.close()      def handle_read(self):         data = self.recv(1024)         if data:             print "received ", data         self.send("hello client")  c = client('127.0.0.1', 5007) asyncore.loop() 

result:

execute server.py:

waiting connection... 

then client.py:

client start... received  hello server client: connection closed client: connection closed 

finally client.py exited, , there 1 more line displayed in ouput window of server.py , server keeps running:

connection ('127.0.0.1', 58197) 

there cannot understand:

1. why function handle_closed in client.py executed twice?

2. why isn't function handle_reading in server.py executed? client.py has sent message("hello client"), why cannot server receive it?

3. why isn't function handle_closed in server.py executed? want execute codes in server.py when client exits, seems nothing handle_closed in server.py?

asyncore talk

the handle_read() in server.py never called.

but why?! it's server class...

yes, server class uses socket listening non-established connections. reads on go handle_accept(), actual channel sockets (connected endpoint) should given new instance of dispatcher-inherited class (preferably). in server's handle_accept() method sockets got accept() local , deleted upon exiting function, so: new connection accepted, text sent , after socket killed.

have read on asyncore module , my answer in other question.

server

you need to, said, make new class connections in server.py:

class clienthandler(asyncore.dispatcher):     def handle_read(self):         data = self.recv(1024)         if not data:             return         print "received:", data      def handle_close(self):         print "server: connection closed"         self.close() 

note here reading don't need manually close socket when null recieved - asyncore takes care of closing connection.

then have instantiate in server when connection made:

    def handle_accept(self):         ...         clienthandler(socket) 

you made spelling mistake in server - method's proper name handle_close. though wouldn't useful. client-connection related in clienthandler.

client

in client.py need modify handle_read():

    if data:         print "received ", data 

change to:

    if not data:         return     print "received ", data 

why? without send() called when socket closed, resulting in handle_close() being called second time, asyncore. said - asyncore takes care of this.

notes

now can write more complex server-side class connections. learn how os-level sockets work, won't trouble.

asyncore pretty nice wrapper sockets, if want higher-lever things, http or smtp processing in event-driven environment, twisted library interest you!