04-05-2011 11:01 PM
I am trying to send a message between to computers on a network using Multicast UDP. I receive no errors, but the message does not get to the receiver. I was able to get a regular UDP message between them, but not a multicast. I have the address set to a valid multicast address and I have the TTL set to higher than the number of hops. What could I be missing?
04-06-2011 02:36 AM
have you tried to achieve that task using the UDP multicast examples coming with LabVIEW?
Usually I start with them and then change them to fit my needs...
04-06-2011 06:56 AM
Yes, I have tried the examples. Have you successfully used them between two different computers? They work fine for me on the same computer, but not remotely. I know the number of hops (1) between the two computers because they are on the same switch and just for fun I verified it with tracert.
04-06-2011 07:15 AM
yes, the examples work for me (read/write on different computers, with several switches in between)...
04-06-2011 07:36 AM
First (and only) thought:
Is the UDP mutilcast propgated beyond the local subnet?
I seem to rember they were not routed.
04-06-2011 02:50 PM
Have you double checked your network and router firewall settings? It sounds like the router might not be passing the message on. Also, is there a reason that you are using UDP specifically?
04-06-2011 03:08 PM - edited 04-06-2011 03:09 PM
Both computers are on a simple Netgear switch, so I don't think that is the issue. My guess is that it is a firewall/IT "protection" problem. I plan on trying it tonight at home to see if I can get it to work off the corporate network.
The purpose for using multicast UDP was:
I picked multicast UDP because of its ability to broadcast data without worry about who was receiving it.
04-06-2011 05:03 PM
I've decided to go a different route. I'm going to use regular UDP with a request/response architecture. I know that this method works, it looks to be more efficient, and I won't have to worry about number of hops. Thanks for everyones input.
01-02-2012 02:03 PM
Well, I've got the same problem. Unfortunately, I must use multicast.
I am using the multicast send example VI on one PC, and the multicast receive example VI on another. The 2 PCs are directly connected with an Ethernet cable. Wireshark running on the receive PC sees the multicast UDP packets, but the receive VI does not. If I also run the send example on the receive PC, then all of a sudden the receive VI gets both the multicast packets from both senders.
I have turned the firewall off on both machines. One machine is XP, the other is Windows 7. Any ideas?
Similar experiments with Java do not exhibit this strange behavior.