Java Multicast Sending Data, Not Receiving

Question

I am writing a class in Java which is used to greatly simplify the process of multicasting. However, I am having two big problems with it:

1. The class sends data

Answer 1

I've run into similar problems before and had to ensure that the NetworkInterface was specified on the receiving side.

SocketAddress socketAddress = new SocketAddress(groupIp, groupPort);
NetworkInterface networkInterface = NetworkInterface.getByName(interfaceName);

socket.joinGroup(socketAddress, networkInterface);

Where interfaceName is one of the interface names shown when running ifconfig on Linux or Mac.