www.pudn.com > jnp-src.rar > DNSQuery.java

/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.io.*; 
import java.util.*; 
 
public class DNSQuery { 
  private String queryHost; 
  private int queryType, queryClass, queryID; 
  private static int globalID; 
 
  public DNSQuery (String host, int type, int clas) { 
    StringTokenizer labels = new StringTokenizer (host, "."); 
    while (labels.hasMoreTokens ()) 
      if (labels.nextToken ().length () > 63) 
        throw new IllegalArgumentException ("Invalid hostname: " + host); 
    queryHost = host; 
    queryType = type; 
    queryClass = clas; 
    synchronized (getClass ()) { 
      queryID = (++ globalID) % 65536; 
    } 
  } 
 
  public String getQueryHost () { 
    return queryHost; 
  } 
 
  public int getQueryType () { 
    return queryType; 
  } 
 
  public int getQueryClass () { 
    return queryClass; 
  } 
 
  public int getQueryID () { 
    return queryID; 
  } 
 
  public byte[] extractQuery () { 
    ByteArrayOutputStream byteArrayOut = new ByteArrayOutputStream (); 
    DataOutputStream dataOut = new DataOutputStream (byteArrayOut); 
    try { 
      dataOut.writeShort (queryID); 
      dataOut.writeShort ((0 << DNS.SHIFT_QUERY) | 
                          (DNS.OPCODE_QUERY << DNS.SHIFT_OPCODE) | 
                          (1 << DNS.SHIFT_RECURSE_PLEASE)); 
      dataOut.writeShort (1); // # queries 
      dataOut.writeShort (0); // # answers 
      dataOut.writeShort (0); // # authorities 
      dataOut.writeShort (0); // # additional 
      StringTokenizer labels = new StringTokenizer (queryHost, "."); 
      while (labels.hasMoreTokens ()) { 
        String label = labels.nextToken (); 
        dataOut.writeByte (label.length ()); 
        dataOut.writeBytes (label); 
      } 
      dataOut.writeByte (0); 
      dataOut.writeShort (queryType); 
      dataOut.writeShort (queryClass); 
    } catch (IOException ignored) { 
    } 
    return byteArrayOut.toByteArray (); 
  } 
 
  private Vector answers = new Vector (); 
  private Vector authorities = new Vector (); 
  private Vector additional = new Vector (); 
 
  public void receiveResponse (byte[] data, int length) throws IOException { 
    DNSInputStream dnsIn = new DNSInputStream (data, 0, length); 
    int id = dnsIn.readShort (); 
    if (id != queryID) 
      throw new IOException ("ID does not match request"); 
    int flags = dnsIn.readShort (); 
    decodeFlags (flags); 
    int numQueries = dnsIn.readShort (); 
    int numAnswers = dnsIn.readShort (); 
    int numAuthorities = dnsIn.readShort (); 
    int numAdditional = dnsIn.readShort (); 
    while (numQueries -- > 0) { // discard questions 
      String queryName = dnsIn.readDomainName (); 
      int queryType = dnsIn.readShort (); 
      int queryClass = dnsIn.readShort (); 
    } 
    try { 
      while (numAnswers -- > 0) 
        answers.addElement (dnsIn.readRR ()); 
      while (numAuthorities -- > 0) 
        authorities.addElement (dnsIn.readRR ()); 
      while (numAdditional -- > 0) 
        additional.addElement (dnsIn.readRR ()); 
    } catch (EOFException ex) { 
      if (!truncated) 
        throw ex; 
    } 
  } 
 
  private boolean authoritative, truncated, recursive; 
 
  protected void decodeFlags (int flags) throws IOException { 
    boolean isResponse = ((flags >> DNS.SHIFT_QUERY) & 1) != 0; 
    if (!isResponse) 
      throw new IOException ("Response flag not set"); 
    int opcode = (flags >> DNS.SHIFT_OPCODE) & 15; 
    // could check opcode 
    authoritative = ((flags >> DNS.SHIFT_AUTHORITATIVE) & 1) != 0; 
    truncated = ((flags >> DNS.SHIFT_TRUNCATED) & 1) != 0; 
    boolean recurseRequest = ((flags >> DNS.SHIFT_RECURSE_PLEASE) & 1) != 0; 
    // could check recurse request 
    recursive = ((flags >> DNS.SHIFT_RECURSE_AVAILABLE) & 1) != 0; 
    int code = (flags >> DNS.SHIFT_RESPONSE_CODE) & 15; 
    if (code != 0) 
      throw new IOException (DNS.codeName (code) + " (" + code + ")"); 
  } 
   
  public boolean isAuthoritative () { 
    return authoritative; 
  } 
 
  public boolean isTruncated () { 
    return truncated; 
  } 
 
  public boolean isRecursive () { 
    return recursive; 
  } 
 
  public Enumeration getAnswers () { 
    return answers.elements (); 
  } 
 
  public Enumeration getAuthorities () { 
    return authorities.elements (); 
  } 
 
  public Enumeration getAdditional () { 
    return additional.elements (); 
  } 
}