Test of loopback interfaces

loopback_test.py

import socket
import struct
import time

group = '224.1.1.4'
test_interfaces = [
    '127.0.0.1', 
    # Fill in an interface of your own computer here
    '192.168.42.42']

port = 15007

def send_no_join(interface):
    print(f"No join test from {group} {interface}")
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 1)
    sock.setsockopt(
        socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface))

    data = f"multicast send - group: {group} interface: {interface}"
    data = data.encode()

    try:
        sock.sendto(data, (group, port))
    except socket.timeout:
        pass
    except OSError as e:
       print(e)

def send_with_join(interface):
    print(f"With join test from {group} {interface}")
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 1)
    sock.setsockopt(
        socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface))
    mreq = struct.pack(
        "4s4s", socket.inet_aton(group),
        socket.inet_aton(interface))
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

    data = f"multicast send - group: {group} interface: {interface}"
    data = data.encode()

    try:
        sock.sendto(data, (group, port))
    except socket.timeout:
        pass
    except OSError as e:
       print(e)


for test_interface in test_interfaces:
    send_no_join(test_interface)
    time.sleep(0.5)

for test_interface in test_interfaces:
    send_with_join(test_interface)
    time.sleep(0.5)