java 开发的局域网内DNS 服务器

package util; import java.util.*; import java.net.*; public class Dns { private Vector<String> answername = null; private Vector<InetAddress> answerip = null; static byte[] QueryDomain(String domain) { String[] StringSplit = domain.split("\\."); String DomainFormat = ""; for (int i = 0; i < StringSplit.length; i++) { DomainFormat = DomainFormat + (Character.toString((char) StringSplit[i].length()) + StringSplit[i]); } return (DomainFormat + Character.toString((char) 0)).getBytes(); } public void opet() { InetAddress url = null; DatagramSocket ds = null; try { url = ByteArray.strtourl("202.97.224.68"); } catch (Exception urlException) { System.out.println(urlException); } try { ds = new DatagramSocket(8888); } catch (Exception BlindError) { System.out.println(BlindError + "udp无法使用端口"); } byte[] b = new byte[1024]; DatagramPacket dpr = new DatagramPacket(b, 1024); short Flags = 0x0100; short Questions = 0x0001; short AnswerRRs = 0x0000; short AuthorityRRs = 0x0000; short AdditionalRRs = 0x0000; short SEARCHTYPE = 1; short SEARCHCLASS = 0x0001; // Class 一般为 1 指 Internet // 构造请求报文 ByteArray ba = new ByteArray(); ba.add((short) 20); ba.add(Flags); ba.add(Questions); ba.add(AnswerRRs); ba.add(AuthorityRRs); ba.add(AdditionalRRs); ba.add(QueryDomain("www.baidu.com")); ba.add(SEARCHTYPE); ba.add(SEARCHCLASS); byte[] Header = ba.getBytes(); ba = null; try { ds.setSoTimeout(6000); ds.send(new DatagramPacket(Header, Header.length, url, 53)); ds.receive(dpr); } catch (Exception e) { System.out.println(e); } System.out.println("TID is OK"); if ((ByteArray.bytes2short(b, 2) & 0x000f) != 0) { System.out .print("Error the domain you request is can't to explain!!"); } answername = new Vector<String>(); answerip = new Vector<InetAddress>(); int answers = ByteArray.bytes2short(b, 6); System.out.println("Answers:" + answers); int answercount = 0; // [4:6]Questions 数 两个字节 // [6:8]Answer RRs数 两个字节 // [8:10]Authority RRs数 两个字节 // [10:12]Additional RRs数 两个字节 int bitflag = 12; while (b[bitflag] != 0) bitflag++; bitflag++; // 域名结束 bitflag += 2; // 跳过Type bitflag += 2; // 跳过Class int i = 0; while (i < answers) { System.out.println("============" + (i + 1) + "=============="); // Name 两个字节 指针-指向域名的字符 bitflag += 2; if (ByteArray.bytes2short(b, bitflag) == 1) { // Type 两个字节 bitflag += 8; // Class两个字节 // TTL 四个字节 bitflag += 2; // Rdatalength 两个字节 System.out.println(ByteArray.unsignedByte(b[bitflag]) + "." + ByteArray.unsignedByte(b[bitflag + 1]) + "." + ByteArray.unsignedByte(b[bitflag + 2]) + "." + ByteArray.unsignedByte(b[bitflag + 3])); answerip.add(ByteArray.strtourl(ByteArray .unsignedByte(b[bitflag]) + "." + ByteArray.unsignedByte(b[bitflag + 1]) + "." + ByteArray.unsignedByte(b[bitflag + 2]) + "." + ByteArray.unsignedByte(b[bitflag + 3]))); bitflag += 4; } else if (ByteArray.bytes2short(b, bitflag) == 5) // CNAME { bitflag += 8; int rdatalength = ByteArray.bytes2short(b, bitflag); bitflag += 2; StringBuffer domain = new StringBuffer(); getDomain(b, bitflag, domain); System.out.println(domain.toString()); answername.add(domain.toString()); bitflag += rdatalength; } i++; } } public void getDomain(byte[] b, int offset, StringBuffer domain) { if ((b[offset] & 0xc0) == 0xc0) { getDomain(b, ByteArray.bytes2short(b, offset) & 0x3fff, domain); } else if (b[offset] == 0) { } else { domain.append(new String(b, offset + 1, ByteArray .unsignedByte(b[offset])) + "."); getDomain(b, offset + 1 + ByteArray.unsignedByte(b[offset]), domain); } } }