// serialize the endpoint to a SocketAddress and create an array to hold the values.  Pin the array.
SocketAddress socketAddress = ipEndPoint.Serialize();
byte[] socketBytes = new byte[socketAddress.Size];
GCHandle handleSocketAddress = GCHandle.Alloc(socketBytes, GCHandleType.Pinned);

// Should copy the first 16 bytes (the SocketAddress has a 32 byte buffer, the size will only be 16, which is what the SOCKADDR accepts
for (int i = 0; i < socketAddress.Size; ++i)
{
    socketBytes[i] = socketAddress[i];
}