Python in a Nutshell

Name

send

Synopsis

                           d.send(data)

In class dispatcher_with_send, method d .send is equivalent to a socket object’s method send_all in that it sends all the data. However, d .send does not send all the data at once and does not block; rather, d sends the data in small packets of 512 bytes each in response to handle_write events (callbacks). This strategy ensures good performance in simple cases.

Example 19-7 uses module asyncore to reimplement the server of Example 19-1, with the added ability to serve any number of clients simultaneously.

Example 19-7. Asynchronous TCP echo server using asyncore

import asyncore
import socket

class MainServerSocket(asyncore.dispatcher):
    def __init_  _(self, port):
        asyncore.dispatcher.__init_  _(self)
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.bind(('',port))
        self.listen(5)
    def handle_accept(self):
        newSocket, address = self.accept( )
        print "Connected from", address
        SecondaryServerSocket(newSocket)

class SecondaryServerSocket(asyncore.dispatcher_with_send):
    def handle_read(self):
        receivedData = self.recv(8192)
        if receivedData: self.send(receivedData)
        else: self.close( )
    def handle_close(self):
        print "Disconnected from", self.getpeername( )

MainServerSocket(8881)
asyncore.loop( )

The complexity of Example 19-7 is modest, comparable with that of Example 19-1. The additional functionality of serving multiple clients simultaneously, with the high performance and scalability of asynchronous event-driven programming, comes quite cheaply thanks to ...