Java学习篇之--检测主机是否在线Ping

Ping技术哪家强？

        最近想写个程序，检测一下远程主机是否在线，因而在网上找到了不少前辈的方法，如今总结一下，分享给你们，但愿可以抛砖引玉：

        方法一：利用java.net包中的类InetAddress中的getByAddress()方法：

函数原型：
public static InetAddress getByAddress(byte[] addr)
                                throws UnknownHostException

public boolean isReachable(int timeout)
                    throws IOException

注释： Test whether that address is reachable.

       

源码：
package com.ryze.ping.test;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class PingTest {

	public static void main(String[] args) throws UnknownHostException, IOException {
		InetAddress inet;
		inet = InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 });
		System.out.println("Sending Ping Request to " + inet);
		System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

		inet = InetAddress.getByAddress(new byte[] { (byte) 220, (byte) 181, 112, (byte)244 });
		System.out.println("Sending Ping Request to " + inet);
		System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
	}
}

运行结果：
Sending Ping Request to /127.0.0.1
Host is reachable
Sending Ping Request to /220.181.112.244
Host is NOT reachable

        方法二：利用java.net包中的类InetAddress中的getByName()方法：

函数原型：
public static InetAddress getByName(String host)
                             throws UnknownHostException

源码：
package com.ryze.ping.test;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class PingTest {

	public static void main(String[] args) throws UnknownHostException, IOException {
	    String ipAddress = "127.0.0.1";
	    InetAddress inet = InetAddress.getByName(ipAddress);

	    System.out.println("Sending Ping Request to " + ipAddress);
	    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

	    ipAddress = "220.181.112.244";
	    inet = InetAddress.getByName(ipAddress);

	    System.out.println("Sending Ping Request to " + ipAddress);
	    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
	}
}

运行结果：
Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 220.181.112.244
Host is NOT reachable

        方法三：利用java.lang包中的类Runtime中的getRuntime()方法：

函数原型：
public static Runtime getRuntime()

注释： returns the runtime object associated with the current Java application.

函数原型：
public Process exec(String command)
             throws IOException

注释： Executes the specified string command in a separate process.

函数原型：
public abstract int waitFor()
                     throws InterruptedException

注释： the exit value of the subprocess represented by this  Process  object. By convention, the value  0  indicates normal termination.

源码：
package com.ryze.ping.test;

public class PingTest {

	public static void main(String[] args) {
			    
	    boolean reachable = false;
	    Process process;
	    try {
	    	String ipAddress = "127.0.0.1";
			process = Runtime.getRuntime().exec("ping " + ipAddress);
			int returnVal = process.waitFor();
			reachable = returnVal == 0?true:false;
			System.out.println("Sending Ping Request to " + ipAddress);
			System.out.println(reachable ? "Host is reachable" : "Host is NOT reachable");
			
			ipAddress = "220.181.112.244";
			process = Runtime.getRuntime().exec("ping " + ipAddress);
			returnVal = process.waitFor();
			reachable = returnVal == 0?true:false;
			System.out.println("Sending Ping Request to " + ipAddress);
			System.out.println(reachable ? "Host is reachable" : "Host is NOT reachable");
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

运行结果：
Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 220.181.112.244
Host is reachable

        小结：经过google搜索加上本身亲自实验，发现前两种方法只能ping通局域网内的Ip，对于外网的ip通常ping不通，第三种方法个人理解是至关于在本地DOS环境下进行ping，能ping通外网，可是每ping一次效率很低。