io_model.py

import select
import socket
import time


class EventHandler:
    def fileno(self):
        raise NotImplementedError()

    def wants_to_receive(self):
        return False

    def handle_receive(self):
        pass

    def wants_to_send(self):
        return False

    def handle_send(self):
        pass


def event_loop(handlers):
    while True:
        wants_recv = [h for h in handlers if h.wants_to_receive()]
        wants_send = [h for h in handlers if h.wants_to_send()]
        can_recv, can_send, _ = select.select(wants_recv, wants_send, [])
        for h in can_recv:
            h.handle_receive()
        for h in can_send:
            h.handle_send()


class UDPServer(EventHandler):
    def __init__(self, address):
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.sock.bind(address)

    def fileno(self):
        return self.sock.fileno()

    def wants_to_receive(self):
        return True


class UDPTimeServer(UDPServer):

    def handle_receive(self):
        msg, addr = self.sock.recvfrom(1)
        self.sock.sendto(time.ctime().encode('ascii'), addr)


class UDPEchoServer(UDPServer):
    def handle_receive(self):
        msg, addr = self.sock.recvfrom(8192)
        self.sock.sendto(msg, addr)


if __name__ == '__main__':
    handlers = [UDPTimeServer(('', 14000)), UDPEchoServer(('', 15000))]
    event_loop(handlers)
    import asyncio

    el = asyncio.get_event_loop()
    asyncio.get_event_loop_policy()