java端口扫描（原创）

　　项目需要扫描占用的端口来判断服务是否启动，通过查资料发现大多数方法都是ServerSocket socket = new ServerSocket(port);代码如下：

package com.frank.util;

import java.io.IOException;

import java.net.InetAddress;

import java.net.Socket;

import java.net.UnknownHostException;

public class NetUtil {

    /***

     *  true:already in using  false:not using

     * @param port

     */

    public static boolean isLoclePortUsing(int port){

        boolean flag = true;

        try {

            flag = isPortUsing("127.0.0.1", port);

        } catch (Exception e) {

        }

        return flag;

    }

    /***

     *  true:already in using  false:not using

     * @param host

     * @param port

     * @throws UnknownHostException

     */

    public static boolean isPortUsing(String host,int port) throws UnknownHostException{

        boolean flag = false;

        InetAddress theAddress = InetAddress.getByName(host);

        try {

            Socket socket = new Socket(theAddress,port);

            flag = true;

        } catch (IOException e) {

        }

        return flag;

    }

}

　　经过测试发现如果端口没有占用，此方法的时间消耗比较大，大概在1s左右，如果是循环扫描端口，无疑是无法接受的。

可以用java.net.ServerSocket包的ServerSocket代替Socket去检测端口，方法如下：

  public static boolean isPortUsing(String host,int port) throws UnknownHostException{

      boolean flag = true;

//      InetAddress theAddress = InetAddress.getByName(host);

      try {

//          Socket socket = new Socket(theAddress,port);

    	  ServerSocket socket = new ServerSocket(port);

          flag = false;

          socket.close();

      } catch (IOException e) {

      }

      return flag;

  }

　　对Socket等知识研究较少，如有问题，请大家及时提出，尽快改正，谢谢！