Using multicast socket in Ad-hoc network yelds: [Errno 19] No such device

Question

I want to create a multicast socket connection in a ad-hoc network topology. I have a client/server implementation in python that is WORKING FINE on a normal network configuration, meaning a standard network config with internet connection.
This is the code for the client connector, the "subscriber":

if __name__ == "__main__":
    multicast_group = '224.0.0.1'
    server_address = ('', 10000)

    # Create the socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

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

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

In a normal, internet connected network, this works fine, but in an ad-hoc network topology, this throws the error:

File "main.py" line 33
setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
File "usr/lib/python2.7/socket.py", line 228, in meth
return getattr(self.__sock, name)(*args)
socket.error: [Error 19] No such device

Any ideas what is happening?
Thanks

Answer 1

A working solution is to manually set your network interface for socket to use:

sock.setsockopt(socket.SOL_SOCKET, 25, 'bat0')

And add membership to the group and hostname:

group = socket.inet_aton(multicast_group)
intf = socket.gethostbyname(socket.gethostname())

sock.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, group + socket.inet_aton(intf))