程序|多线程扫描500个IP10秒钟左右, 一个IP等待0.3秒
说来惭愧, 我觉得是用java写的过程编程, 少贴一点仅供参考:
package steeven;

import java.sql.*;
import java.io.*;
import java.util.*;
import java.text.*;
import javax.servlet.http.*;

public class Ip extends Common implements Runnable{

  public String ip;           // IP, 用户名, 主机名

  ResultSet list;                 // 分页显示的记录集
  public Ip cur;               // 分页显示的当前记录

  static public Hashtable ping = new Hashtable(); //ping 后的结果集
  static int threadCount = 0;  //当前线程的数量, 防止过多线程摧毁电脑


  public Ip() {}
  public Ip(String ip){
    this.ip=ip;
    Thread r = new Thread(this);
    r.start();
  }

  public static void Ping(String ip) throws Exception{
    //最多30个线程
    while(threadCount>30)
      Thread.sleep(50);
    threadCount +=1;
    Ip p = new Ip(ip);
  }
  public void PingAll() throws Exception{
    threadCount =0;
    ping = new Hashtable();
    while(next())  //next()对所有局域网Ip放到cur
      Ping(cur.ip);
    //等着所有Ping结束
    while(threadCount>0)
      Thread.sleep(50);
  }
  public void run(){
    try{
      Process p= Runtime.getRuntime().exec ("ping "+ip+ " -w 300 -n 1");
      InputStreamReader ir = new InputStreamReader(p.getInputStream());
      LineNumberReader input = new LineNumberReader (ir);
      //读取结果行
      for (int i=1 ; i<7; i++)
        input.readLine();
      String line= input.readLine();
      
      if (line.length()<17 || line.substring(8,17).equals("timed out"))
        ping.put(ip,new Boolean(false));
      else
        ping.put(ip,new Boolean(true));
      //线程结束
      threadCount -= 1;
    }catch (IOException e){}
  }
  public static void main(String[] args) throws Exception{
    Ip ip= new Ip();
    ip.PingAll();
    java.util.Enumeration key = ping.keys();
    String k;
    while((k = (String)key.nextElement()) != null)
      System.out.println(k+": "+ping.get(k));
  }
}

1. 利用Ping比较愚蠢, 但是相对简单些
2. 如果Ping 成功后, 用nbtstat还可以得到主机名, 当前用户名, MAC地址...一切尽在掌握中  :)