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multicast join question

We have a product that utilizes multicast to distribute near-real-time status updates to clients.  This is a windows application that has been around for a while .  Some customer sites struggle to get multicast setup correctly on their network, and are asking if there is something more we can do as a vendor to help them.  


In the latest troubleshooting from one site, they are suggesting that we don't properly notify the Cisco routers that a client is joining the multicast domain and wishes to receive the multicast traffic.   I am not a Cisco expert, so I decided to post my question here.  They said they have configured the router for PIMS First Sparse Mode, and watching via wireshark, they cannot see the join request.  


On the software side, we are issuing calls to Microsoft WINSOCK setsockopt to IP_ADD_MEMBERSHIP which says it will "Join the socket to the supplied multicast group on the specified interface".  We have used a 3rd party app to confirm that multicast "send" and "receive" app is also not passing through the router(s).   


This same code works on hundreds of other (different) customer sites, so it's most likely a networking configuration concern at this location, but I am wondering if we as a vendor can do something more, or different, to make this easier for all of our customers.  


Is it time to give up on multicast and move to unicast for everything?  Is there some way to help our customers troubleshoot this quickly?  


Thanks for any thoughts you might have...


Re: multicast join question

Quick update.  Breaking the Microsoft NIC team and resetting the IP stack has seemed to help.  We are able to see the Multicast join via Wireshark.  Now I need to convince the site that their router config is not working.  


I need some tips on how to troubleshot this in the router.  I have no access to this.

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