multicastUDP_receiver.py

import socket
import struct
import sys
from datetime import datetime
import queue

# ip address of network interface
MCAST_IF_IP = '192.168.178.38'

multicast_group = '230.120.10.2'
server_address = ('', 8123)

def start(filter = None):
    # Create the socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

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

    print("Start")

    # Tell the operating system to add the socket to the multicast group
    # on all interfaces.
    group = socket.inet_aton(multicast_group)
    mreq = struct.pack('4s4s', group, socket.inet_aton(MCAST_IF_IP))
    sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

    print("Ready")
    saveCounter = 0

    buffer = queue.Queue(20)

    # Receive/respond loop
    while True:
        data, address = sock.recvfrom(1024)
        data_str = data.decode("utf-8").strip()
        if filter is not None and filter not in data_str:
            continue
        data_str = "[" + str(address[0]) + " - " + datetime.now().strftime('%b-%d-%Y_%H:%M:%S') + "] " + data_str
        print(data_str)
        buffer.put(data_str)
        if buffer.full():
            buffer.get()


        if "NTP-Update not successful" in data_str or "Start program" in data_str:
            f = open("log.txt",'a')
            while not buffer.empty():    
                f.write(buffer.get())
                f.write("\n")
            f.close()
            saveCounter = 20
            
        if saveCounter > 0:
            f = open("log.txt",'a')
            f.write(data_str)
            f.write("\n")
            if saveCounter == 1:
                f.write("\n")
            f.close()
            saveCounter -= 1


# Main
if __name__ == '__main__':

    # Check if a filter is given
    # use filter as argument to filter messages: python3 multicastUDP_receiver.py "filter"

    if len(sys.argv) > 1:
        start(sys.argv[1])
    else:
        start()