Open Source Multicast to Unicast Converter

I’ve been put in a position where I have to do this, and this isn’t really my forte.

I’ve got a service (let’s call it Service X) which I have to basically proxy multicast packets from and to. Service X is written by a third-party and we don’t have access to source code.

Service X accepts client connections in a traditional client/server model. However, for annoying reasons, our router is going to be multicasting the client connections, which Service X doesn’t handle. So, I’ll need a piece of software which can join a multicast group, and then forward the packets to/from Service X.

Any ideas? I’ve been looking around the Apache website, but I can’t find anything, and my google-fu is failing here. It has to be open source for cost reasons.

Thanks for the help.