__init__.py

import errno
import socket
import select


class EventLoop(object):
    def __init__(self):
        self.callbacks = []
        self.sources = []
        self.handlers = {}

    def add_handler(self, fd, callback):
        self.handlers[fd] = callback
        self.sources.append(fd)

    def start(self):
        poll_timeout = 0.2

        while True:
            self._running = True
            r, w, _ = select.select(self.sources, [], [], poll_timeout)
            for fd in r:
                print fd
                if fd in self.handlers:
                    self.handlers[fd]('READ')


class EchoServer(object):
    def __init__(self, eventloop):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
        self.socket.setblocking(0)
        self.socket.bind(('localhost', 9999))
        self.socket.listen(2)
        self.eventloop = eventloop

    def start(self):
        self.eventloop.add_handler(self.socket.fileno(), self.handle_event)

    def handle_event(self, event):
        conn, addr = self.socket.accept()
        try:
            print conn.recv(4096)
        except socket.error, e:
            if e.errno in (errno.EWOULDBLOCK, errno.EAGAIN):
                print 'whops', e
                return
            raise


if __name__ == '__main__':
    loop = EventLoop()
    server = EchoServer(loop)
    server.start()
    loop.start()