Search devices on all networks

问题:

I want to implement a code through which i can list-up upnp compliant media renderer devices connected on network. I googled for this and found following code on twisted website

When 2 networks(ethernet and wifi) are connected on my machine, it lists up devices of only one network.

code

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor
import re

class MulticastPingPong(DatagramProtocol):
    XMLNS = "{urn:schemas-upnp-org:device-1-0}"

    def startProtocol(self):
        # Join the multicast address, so we can receive replies:
        self.transport.joinGroup("239.255.255.250")

    def datagramReceived(self, datagram, address):
        if(re.search("USN:.*MediaRenderer", datagram, flags=re.IGNORECASE)):
            # code to print friendly name

reactor.listenMulticast(1900, MulticastPingPong(), listenMultiple=True)
reactor.run()

How to search devices of multiple networks ?