Python - Bind Error On Multicast Bind On Windows

I need to use multicast in Python application, after googling a bit I found snippets of code that works, here it is: # UDP multicast examples, Hugo Vincent, 2005-05-14. import sock

Solution 1:

As noted by Carl Cerecke in the comments of the PYMOTW Multicast article, the use of socket.INADDR_ANY in Windows will bind to the default multicast address and if you have more than one interface Windows has the potential to pick the wrong one.

In order to get around this, you can explicitly specify the interface you want to receive multicast messages from:

group = socket.inet_aton(multicast_group)
iface = socket.inet_aton('192.168.1.10') # listen for multicast packets on this interface.
sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, group+iface)

You can get a list of interfaces using the following:

socket.gethostbyname_ex(socket.gethostname()) 
# ("PCName", [], ["169.254.80.80", "192.168.1.10"])

In the above example, we would likely want to skip over the first 169.254 link-local address and select the desired 192.168.1.10 address.

socket.gethostbyname_ex(socket.gethostname())[2][1]
# "192.168.1.10"