Socket I/O Multiplexing

demo_client.py

import sys
import socket
from time import sleep
from threading import Thread

SERVER = '127.0.0.1'
PORT = 9999

def client(timeout=0):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        try:
            sock.connect((SERVER, PORT))
        except:
            sys.exit(sys.exc_info()[1])

        try:
            if sock.sendall(b'hello') is not None:
                sock.shutdown(socket.SHUT_WR)
        except:
            sys.exit(sys.exc_info()[1])
        else:
            sleep(timeout)

if __name__ == '__main__':
    c1 = Thread(target=client, args=(3,))
    c2 = Thread(target=client, args=(1,))
    c3 = Thread(target=client)
    c1.start()
    c2.start()
    c3.start()

demo_select.py

import sys
import socket
import select

HOST = '127.0.0.1'
PORT = 9999

fd_to_socket = {}

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
    sock.bind((HOST, PORT))
    sock.listen(5)
    print("Server is listening at {}:{}".format(HOST, PORT))

    sock.setblocking(False)

    poll = select.poll()
    poll.register(sock, select.POLLIN)

    try:
        while True:
            ready = poll.poll()

            if not ready:
                break

            for fd, event in ready:
                if fd == sock.fileno():
                    connection, client_address = sock.accept()
                    print("Accepted from", client_address)

                    fd_to_socket[connection.fileno()] = connection
                    poll.register(connection, select.POLLIN)
                else:
                    connection = fd_to_socket[fd]
                    raw_data = connection.recv(1024)

                    if not raw_data:
                        print("Closed connection to", connection.getpeername())
                        poll.unregister(connection)
                        connection.close()
                        break

                    print("Reveived {} from {}".format(raw_data.decode(), connection.getpeername()))
    except KeyboardInterrupt:
        print("EXIT")
    except:
        print(sys.exc_info()[1])

demo_selectors.py

import sys
import socket
import selectors

HOST = '127.0.0.1'
PORT = 9999

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
    sock.bind((HOST, PORT))
    sock.listen(5)
    print("Server is listening at {}:{}".format(HOST, PORT))
    sock.setblocking(False)

    with selectors.DefaultSelector() as selector:
        selector.register(sock, selectors.EVENT_READ)

        try:
            while True:
                ready = selector.select()

                if not ready:
                    break

                for key, _ in ready:
                    if key.fileobj == sock:
                        try:
                            connection, client_address = sock.accept()
                            print("Accepted from", client_address)
                        except:
                            sys.exc_info()[1]
                        else:
                            selector.register(connection, selectors.EVENT_READ)
                    else:
                        connection = key.fileobj

                        raw_data = connection.recv(1024)

                        if not raw_data:
                            print("Closed connection to", connection.getpeername())
                            selector.unregister(connection)
                            connection.close()
                            break

                        print("Received {} from {}".format(raw_data.decode(), connection.getpeername()))
        except KeyboardInterrupt:
            print("EXIT")
        except:
            sys.exc_info()[1]