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！