I am working on developing an onvif device manager, more specifically the discovery part. To be able to connect over the internet, I need a python script on the local network’s server (debian12). The script is working if I run it om my windows 10 pc but not on my ubuntu 22 pc.

Here is my code:

def Discovery():
    multicast_ip = "239.255.255.250"
    multicast_port = 3702

    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
    my_ip = get_my_ip()
    s.bind((my_ip, 0))
    s.settimeout(2.0)
    
    ret_value = []
    # for i in range(2):
    xml_str = get_soap(0)
    s.sendto(xml_str.encode(), (multicast_ip, multicast_port))
    count = 0
    while True:
        try:
            data, address = s.recvfrom(65535)
            found = False
            for item in ret_value:
                if item[0][0] == address[0]:
                    found = True
                    break
            if found == True:
                continue
            ret_value.append((address, data))
            count += 1
            if count == 5:
                break
        except Exception as e:
            ret_value = e
            break
    s.close()
    return ret_value


if __name__ == '__main__':
    data = Discovery()
    print(data)

With WireShark I can see the request and the anwsers from both clients. The execution never returns from s.recvfrom if timeout not is set. I also tryed s.recvfrom_into. What can be wrong? Any ideas?