Oct 18, 2004 Open Settings - Preferences, select 'Advanced options'. On the left side of the window, go to General Settings - Input. There's an item called 'Network interface address' - type in the IP address of the client network card that you want the client to use when receiving multicast. Press the Save button to store the settings. UDP Multicast using the WP7 API is clearly broken in Windows Phone 8. It is exactly as Morten described, Listening is completely broken. I loaded the Multicast sockets sample from MSDN, which is a rock/scissor/paper game, onto 3 phones running on Wifi to demonstrate the problem. I came across this with my own code and debugged with wireshark.
It is same question as above but for windows.
1 Answer
from a command line:
Displays IP multicast groups that have been joined on one or more interfaces. If an interface is not specified, multicast groups for all interfaces are shown.
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Multicast UDP on raspberry pi
I haven't narrowed things down enough to know if my issue is because of debian, raspbian specifically, or if I am just missing a something completely.
I have a python application that uses multicast UDP to let other devices on the network know that my application is up and running and available at a specific IP address.
The UDP multicast group is 239.255.250.250 and port is 9131. If I run tcpdump, I can see that the packet I am trying to send is actualy sending out data, but I never see anything come through on other machines on the network.
There are other devices that uses this same kind of 'beacon' with same multicast group and port and I can see those packets come through on other machines. The router has no firewall, and I am really kind of out of options at this point.
Below is the basic diagnostics I know how to run. The bad udp chksum looks like it's probably not helpful, but I don't really know anything about that.
Output of ifconfig
Output of tcpdump while app is running
Output of netstat while program is running
4 Answers
I understand that your host, 192.168.2.7 is sending multicast packet to group 239.255.250.250 on port 9131
NOTE: I assume however that servers are listening on port 9131. you didn't provide any info on this.
From ifconfig output, I can see that MULTICAST is enabled and the tcpdump confirm this.
First make sure that the host running the servers (the one receiving the multicast packet) have joined the multicast group.
On each server host type :
If you see your multicast address, it has joined the group.If not, then either something is wrong with your server program or possibly kernel settings.
If the server has joined the group but you don't see any packet incoming from client, then check on your router that you have enabled igmp ( your router must be igmp capable)
For example,on cisco router
If igmp is enabled on router, look for debug features to track the packets.
On server side, start a packet capture :
If you don't see any packet coming in, then the multicast packet are not forwarded (assuming that
Then on client send a multicast packet (use the script in link below to troubleshoot)
NOTE: the UDP packet seems malformed so not sure if servers will be able to read it. You can use the script in link below to confirm whether or not the message in tcpdump are displaying as malformed or not ( they are not in my case)
Example of python code using multicast :
NOTE: I used this script on a debian raspi ( not raspbian and server received packets through router - as setup above - fine)
Linux guide : http://stlinux.com/howto/network/short-guide
Cisco : http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_52_se/configuration/guide/3750scg/swmcast.html#wp1024278
I noticed that this can also be a hardware and/or driver problem. I used multicast UDP (transmit and receive) on my raspberryPI's without any trouble - with C, Java and/or Python programs.
However, I just learned that UDP multicast receive DOES NOT WORK with the nice little USB nano wifi adapter from EDIMAX - sending UDP (multicast) works, also receiving the own (local) messages.
the details of the USB sticks from lsusb:
UDP multicast receive does not work: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
UDP multicast receive works fine: ID 148f:3070 Ralink Technology, Corp. RT2870/RT3070 Wireless Adapter
Windows Multicast Example
I encountered a similar problem where the packets were coming in and I could see them with tcpdump but no program could receive the data.
The problem in this case was that I had used iptables to only permit traffic from my local subnet 192.168.0.0/24 but of course multicast comes from 224.0.0.0/4 instead. Rather than open up that entire subnet (may as well not have a firewall then) I just allowed traffic in from all hosts on the specific UDP port I was using for multicast, and this fixed the problem.
For us we had a similar issue where the multicast group was joined fine, but messages were not being received.
We checked the igmp settings on the router, which seemed to be in order.
In the end we switched from using the IPv6 multicast address to IPv4 and that resolved it for that particular system.