My project develops an analysis tool that collects and sends data over multiple avenues. We are currently trying to develop our software for use on Windows 7 but are running into some issues with collecting and sending data over UDP and Multicast. We have no issues when testing between two XP machines or XP to Vista. For Windows 7, we have tried adding rules to the firewall as well as turning it off completely and the issue still exists. It's obviously something on our programs end that needs to be fixed, but I'm not sure where to start. Does anyone know of any differences between XP, Vista, and Windows 7 regarding UDP and Multicast? Thanks in advance.

I just installed the Reliable Multicast Protocol on the Windows 7 machine. Is this required?

Installing the Reliable Multicast Protocol fixed the issue! I'm a little thrown off that this was not installed by default...thanks for all of the replies. :)

Hello John, I am running into an issue where I have windows 7 machine getting streaming video over a multicast network involving a multicast enabled switch and multicast sender. What I am seeing is that the windows 7 machine starts to get multicast video packets fine, however, it shows random drops of multicast packets. I am also running few windows XP machines which join the same multicast session, however none of them experience these packet losses. My question to you is: when you had this issue which you were able to fix, was this issue related to 1> Joining and receiving a multicast session or 2> you were able to join and receive multicast session, but you were seeing some random losses. I am also curious to understand if your application uses Pragmatic General Multicast (PGM)? Can you please help me understand this better? Thanks, P