public JdpPacketWriter() throws IOException {
  baos=new ByteArrayOutputStream();
  pkt=new DataOutputStream(baos);
  pkt.writeInt(JdpGenericPacket.getMagic());
  pkt.writeShort(JdpGenericPacket.getVersion());
}

public JdpPacketWriter ( ) throws IOException { baos = new ByteArrayOutputStream ( ) ; pkt = new DataOutputStream ( baos ) ; pkt . writeInt ( JdpGenericPacket . getMagic ( ) ) ; pkt . writeShort ( JdpGenericPacket . getVersion ( ) ) ; }
create a jdp packet , add mandatory magic and version headers
