Python3 multicast socket with selectors example

example_mc.py

import socket
import struct
import random
import selectors


MY_ID = random.randint(0, 100)
MC_GROUP = "224.0.0.69"
MC_PORT = 10000

mc_address = (MC_GROUP, MC_PORT)


# Create the socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(
    socket.SOL_SOCKET, socket.SO_REUSEPORT, 1
)  # this line is only required for MacOS

# Bind to the server address
sock.bind(("", MC_PORT))

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


def got_message(sock, mask):
    """Callback function to process multicast packets received."""
    data, address = sock.recvfrom(1024)
    print("GOT", data, "from", address)


# Create selector and register callback
sel = selectors.DefaultSelector()
sel.register(sock, selectors.EVENT_READ, got_message)

# Wait for announces and periodically annouce as a keep alive
print(f"My ID is {MY_ID}")
sock.sendto(f"Hello from {MY_ID}".encode("ascii"), mc_address)
while True:
    events = sel.select(timeout=5)
    for key, mask in events:
        callback = key.data
        callback(key.fileobj, mask)
    if not events:
        #events empty means a timeout was reached
        sock.sendto(f"{MY_ID} is still here".encode("ascii"), mc_address)