java实现Ping示例代码

这个示例不是真正实现ping用来检测是否alive,因为Socket类没有足够操作的权限，但是我们可以模仿ping，通过"echo port"实现，在server端，"echo port"端口一般是7，我们往这个端口写入一个字符串，然后这个server会返回这个字符串。

import java.io.*;
import java.net.*;

public class PseudoPing {
  public static void main(String args[]) {
    try {
      Socket t = new Socket(args[0],7);
      DataInputStream dis = new DataInputStream(t.getInputStream());
      PrintStream ps = new PrintStream(t.getOutputStream());
      ps.println("Hello");
      String str = dis.readLine();
      if (str.equals("Hello"))
        System.out.println("Alive!") ;
      else
        System.out.println("Dead or echo port not responding");              
      t.close();
    }
    catch (IOException e) {
      e.printStackTrace();}
    }
  }
}

import java.io.*;
import java.net.*;

public class ReachableTest {
 public static void main(String args[]) {
     try {
       InetAddress address = InetAddress.getByName("web.mit.edu");
       System.out.println("Name: " + address.getHostName());
       System.out.println("Addr: " + address.getHostAddress());
       System.out.println("Reach: " + address.isReachable(3000));
     }
     catch (UnknownHostException e) {
       System.err.println("Unable to lookup web.mit.edu");
     }
     catch (IOException e) {
       System.err.println("Unable to reach web.mit.edu");
     }
   }
}