event driven io explained

tcpserver.py

# TCP Example

import socket
from eventhandler import EventHandler, event_loop

class TCPServer(EventHandler):
    def __init__(self, address, client_handler, handler_list):
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, True)
        self.sock.bind(address)
        self.sock.listen(1)
        self.client_handler = client_handler
        self.handler_list = handler_list

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

    def wants_to_receive(self):
        return True

    def handle_receive(self):
        client, addr = self.sock.accept()
        # Add the client to the event loop's handler list
        self.handler_list.append(self.client_handler(client, self.handler_list))

class TCPClient(EventHandler):
    def __init__(self, sock, handler_list):
        self.sock = sock
        self.handler_list = handler_list
        self.outgoing = bytearray()

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

    def close(self):
        self.sock.close()
        # Remove myself from the event loop's handler list
        self.handler_list.remove(self)
        
    def wants_to_send(self):
        return True if self.outgoing else False

    def handle_send(self):
        nsent = self.sock.send(self.outgoing)
        self.outgoing = self.outgoing[nsent:]

class TCPEchoClient(TCPClient):
    def wants_to_receive(self):
        return True
    
    def handle_receive(self):
        data = self.sock.recv(8192)
        if not data:
            self.close()
        else:
            self.outgoing.extend(data)

if __name__ == '__main__':
   handlers = []
   handlers.append(TCPServer(('',16000), TCPEchoClient, handlers))
   event_loop(handlers)