A simple multicast sender/listener. Adapted from https://pymotw.com/3/socket/multicast.html to contain both the sender and the listener in the same script.

multicaster.py

#!/usr/bin/env python

import argparse
import datetime
import socket
import struct
import time


def listener(args):
    multicast_group = args.address
    server_address = ("", args.port)

    # Create the socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    # Bind to the server address
    sock.bind(server_address)

    # Tell the operating system to add the socket to
    # the multicast group on all interfaces.
    group = socket.inet_aton(multicast_group)
    mreq = struct.pack("4sL", group, socket.INADDR_ANY)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

    # Receive/respond loop
    while True:
        print("\nwaiting to receive message")
        data, address = sock.recvfrom(1024)

        print(f"received {len(data)} bytes from {address}")
        print(data)

        print(f"sending acknowledgement to {address}")
        sock.sendto(b"ack", address)


def sender(args):
    message = datetime.datetime.today().isoformat()
    multicast_group = (args.address, args.port)

    # Create the datagram socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    # Set a timeout so the socket does not block
    # indefinitely when trying to receive data.
    sock.settimeout(0.2)

    # Set the time-to-live for messages to 1 so they do not
    # go past the local network segment.
    ttl = struct.pack("b", 1)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl)

    try:

        # Send data to the multicast group
        print(f"sending {message}")
        sock.sendto(bytes(message, "utf-8"), multicast_group)

        # Look for responses from all recipients
        while True:
            print("waiting to receive")
            try:
                data, server = sock.recvfrom(16)
            except socket.timeout:
                print("timed out, no more responses")
                break
            else:
                print(f"received {data} from {server}")

    finally:
        print("closing socket")
        sock.close()


if __name__ == "__main__":
    default_address = "224.3.29.71"
    default_port = 10000
    parser = argparse.ArgumentParser(
        description="""A multicast sender/listener.
Adapted from https://pymotw.com/3/socket/multicast.html
to include both the listener and the sender in a single script."""
    )
    parser.add_argument(
        "-a",
        "--address",
        metavar="address",
        type=str,
        help="multicast address to connect to (default = {})".format(default_address),
        default=default_address,
    )
    parser.add_argument(
        "-p",
        "--port",
        metavar="port",
        type=int,
        help="multicast port (default = {})".format(default_port),
        default=default_port,
    )
    parser.add_argument(
        "-l", "--listen", help="listen to multicast traffic", action="store_true"
    )
    parser.add_argument(
        "-s", "--send", help="send multicast traffic", action="store_true"
    )
    args = parser.parse_args()
    if args.listen:
        listener(args)
    elif args.send:
        while True:
            sender(args)
            time.sleep(3.14)
    else:
        parser.print_help()