code: static DatagramSocketImpl createDatagramSocketImpl(boolean isMulticast /*unused on unix*/)
          throws SocketException {
          if (prefixImplClass != null) {
              try {
                  return (DatagramSocketImpl)prefixImplClass.newInstance();
              } catch (Exception e) {
                  throw new SocketException("can't instantiate DatagramSocketImpl");
              }
          } else {
              return new java.net.PlainDatagramSocketImpl();
          }
      }
docs: Creates a new <code>DatagramSocketImpl</code> instance.
  
  @param   isMulticast     true if this impl if for a MutlicastSocket
  @return  a new instance of a <code>DatagramSocketImpl</code>.