code: public void setLoopbackMode(boolean disable) throws SocketException {
          getImpl().setOption(SocketOptions.IP_MULTICAST_LOOP, Boolean.valueOf(disable));
      }
docs: Disable/Enable local loopback of multicast datagrams
  The option is used by the platform's networking code as a hint
  for setting whether multicast data will be looped back to
  the local socket.
  
  <p>Because this option is a hint, applications that want to
  verify what loopback mode is set to should call
  {@link #getLoopbackMode()}
  @param disable {@code true} to disable the LoopbackMode
  @throws SocketException if an error occurs while setting the value
  @since 1.4
  @see #getLoopbackMode