int header_padding = MulticastUtil.BOUNDARY - (pos % MulticastUtil.BOUNDARY);
header_padding = (header_padding == MulticastUtil.BOUNDARY) ? 0 : header_padding;
// skip header_padding bytes anyway, because if no body is
// present, nobody will try to read it
in.skip (header_padding);
// read the GIOP data
byte data[] = new byte[header.packet_length];
if (in.available () < data.length)
{