message_handler.py

class MessageReceiver(object):
    def __init__(self, message_handler):
        self.message_handler = message_handler

    def listen(self):
        pass


class MessageHandler(object):
    def handle_message(self, message):
        pass


import socket
class TcpMessageReceiver(MessageReceiver):
    def __init__(self, message_handler):
        self.MSGLEN = 5

        self.message_handler = message_handler


    def listen(self):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.bind(("127.0.0.1", 9999))
        self.socket.listen(23)

        while True:
            connection, address = self.socket.accept()
            msg = ''
            while len(msg) < self.MSGLEN:
                chunk = connection.recv(self.MSGLEN-len(msg))
                if chunk == '':
                    raise RuntimeError("socket connection broken")
                msg = msg + chunk
            self.message_handler.handle_message(msg)
            connection.close()


class UpperCaseMessageHandler(MessageHandler):
    def handle_message(self, message):
        print str(message).upper()


mr = TcpMessageReceiver(UpperCaseMessageHandler())
mr.listen()