multiplexing-server.py

#!/bin/env python3

import sys
import socket
import selectors
import types

sel = selectors.DefaultSelector()

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)
            set.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:]

host, port = sys.argv[1], int(sys.argv[2])
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)

try:
    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)

except KeyboardInterrupt:
    print("caught keyboard interrupt, exiting")

finally:
    sel.close()