nslookup.java

JAVA网络编程技术内幕一书的源代码

/*
 * 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.net.*;
import java.util.*;

public class NSLookup {
  public static void main (String[] args) {
    if (args.length != 1)
      throw new IllegalArgumentException
        ("Syntax: NSLookup <hostname>[@<nameserver>]");
    int atIdx = args[0].indexOf ("@");
    String nameServer = (atIdx > -1) ? args[0].substring (atIdx + 1) : "ns";
    String hostName = (atIdx > -1) ? args[0].substring (0, atIdx) : args[0];
    System.out.println ("Nameserver: " + nameServer);
    System.out.println ("Request: " + hostName);
    DNSQuery query = new DNSQuery (hostName, DNS.TYPE_ANY, DNS.CLASS_IN);
    try {
      Socket socket = new Socket (nameServer, DNS.DEFAULT_PORT);
      socket.setSoTimeout (10000);
      sendQuery (query, socket);
      getResponse (query, socket);
      socket.close ();
      printRRs (query);
    } catch (IOException ex) {
      System.out.println (ex);
    }
  }
  public static void sendQuery (DNSQuery query, Socket socket) throws IOException {
    BufferedOutputStream bufferedOut =
      new BufferedOutputStream (socket.getOutputStream ());
    DataOutputStream dataOut = new DataOutputStream (bufferedOut);
    byte[] data = query.extractQuery ();
    dataOut.writeShort (data.length);
    dataOut.write (data);
    dataOut.flush ();
  }

  public static void getResponse (DNSQuery query, Socket socket) throws IOException {
    InputStream bufferedIn =
      new BufferedInputStream (socket.getInputStream ());
    DataInputStream dataIn = new DataInputStream (bufferedIn);
    int responseLength = dataIn.readUnsignedShort ();
    byte[] data = new byte[responseLength];
    dataIn.readFully (data);
    query.receiveResponse (data, responseLength);
  }

  public static void printRRs (DNSQuery query) {
    Enumeration answers = query.getAnswers ();
    if (answers.hasMoreElements ())
      System.out.println (query.isAuthoritative () ?
                          "\nAuthoritative answer:\n" :
                          "\nNon-authoritative answer:\n");
    while (answers.hasMoreElements ())
      System.out.println (answers.nextElement ());
    Enumeration authorities = query.getAuthorities ();
    if (authorities.hasMoreElements ())
      System.out.println ("\nAuthoritative answers can be found from:\n");
    while (authorities.hasMoreElements ())
      System.out.println (authorities.nextElement ());
    Enumeration additional = query.getAdditional ();
    if (additional.hasMoreElements ())
      System.out.println ("\nAdditional information:\n");
    while (additional.hasMoreElements ())
      System.out.println (additional.nextElement ());
  }
}