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?
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...
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.
yes, the examples work for me (read/write on different computers, with several switches in between)...
First (and only) thought:
Is the UDP mutilcast propgated beyond the local subnet?
I seem to rember they were not routed.
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?
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.
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.
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.
The behavior you are describing is unusual. Are you running the same version of LabVIEW on both machines? Also, did you modify the multicast send and receive example VIs at all?