java端口扫描（原创）

Posted 2020-06-09

　　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！