main.py

#!/usr/bin/env python3

import selectors
import socket
import types

HOST = socket.gethostbyname(socket.gethostname())
PORT = 65123



def accept_wrapper(sock):
    conn, addr = sock.accept()
    print('Accepted Connection from', addr)
    conn.setblocking(False)
    data = types.SimpleNamespace(addr=addr, inb=b'', outb=b'')
    events = selectors.EVENT_READ | selectors.EVENT_WRITE
    sel.register(conn,events,data=data)

def service_connection(key, mask):
    sock = key.fileobj
    data = key.data
    if mask & selectors.EVENT_READ:
        recv_data = sock.recv(1024)
        if recv_data:
            data.outb += recv_data
        else:
            print('closing connection to', data.addr)
            sel.unregister(sock)
            sock.close()
    if mask & selectors.EVENT_WRITE:
        if data.outb:
            print('echoing', repr(data.outb), 'to', data.addr)
            sent = sock.send(data.outb)
            data.outb = data.outb[sent:]





# Press the green button in the gutter to run the script.
if __name__ == '__main__':
    sel = selectors.DefaultSelector()
    lsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    lsock.bind((HOST, PORT))
    lsock.listen()
    print("Listening on", (HOST,PORT))
    lsock.setblocking(False)
    sel.register(lsock,selectors.EVENT_READ, data=None)

    while True:
        events = sel.select(timeout=None)
        for key, mask in events:
            if key.data is None:
                accept_wrapper(key.fileobj)
            else:
                service_connection(key, mask)

# See PyCharm help at https://www.jetbrains.com/help/pycharm/