Multicasting chat sample

chat.py

#!/usr/bin/env python3
""" Multicasting chat application """
import socket
import struct
import sys
from threading import Thread

MADDX = '225.100.100.100'
PORT = 6543


def listen_messages(is_listening):
    """ Socket listening thread """
    print('Start listening...')
    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        sock.bind(('', PORT))
        ip_mreq = struct.pack('4sl', socket.inet_aton(MADDX), socket.INADDR_ANY)
        sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, ip_mreq)
        sock.settimeout(1)
        while is_listening():
            try:
                print(sock.recv(10240))
                sys.stdout.flush()
            except socket.timeout:
                pass
    print('Stop listening...')


def main():
    """ The program entry point """
    is_listening = False
    name = input('Enter your name: ')

    listening_thread = Thread(target=listen_messages, args=(lambda: is_listening,))
    is_listening = True
    listening_thread.start()

    try:
        with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
            sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
            while is_listening:
                try:
                    line = input()
                    msg = '%s: %s' % (name, line)
                    sock.sendto(msg.encode('utf-8'), (MADDX, PORT))
                except (EOFError, KeyboardInterrupt):
                    is_listening = False
            listening_thread.join()
    except KeyboardInterrupt:
        pass

main()