JAVA使用InetAddress指定端口

Question

我正在使用InetAddress确定我的服务器是否在线。

如果服务器离线，它将重新启动服务器。

此过程每5分钟循环一次，以再次检查服务器是否在线。

它工作得很好，但现在我需要弄清楚如何指定在检查服务器状态时使用端口43594而不是默认的端口80。

谢谢!下面是我的代码：

import java.net.InetAddress;
public class Test extends Thread {
    public static void main(String args[]) {
        try {
            while (true) {
                try
                {
                    InetAddress address = InetAddress.getByName("cloudnine1999.no-ip.org");
                    boolean reachable = address.isReachable(10000);
                    if(reachable){
                        System.out.println("Online");
                    }
                    else{
                        System.out.println("Offline: Restarting Server...");
                        Runtime.getRuntime().exec("cmd /c start start.bat");
                    }
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
                Thread.sleep(5 * 60 * 1000);
            }
        }
        catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

编辑：

好的，我接受了别人的建议，并把它写进了这本书。但现在，当我取消注释此行时..Runtime.getRuntime().exec("cmd /c start start.bat");

我得到了这个错误..

error: unreported exception IOException; must be caught or declared to be thrown

这是我当前的代码：

import java.net.*;
import java.io.*;
public class Test extends Thread {
    public static void main(String args[]) {
        try {
            while (true) {
                SocketAddress sockaddr = new InetSocketAddress("cloudnine1999.no-ip.org", 43594);
                Socket socket = new Socket();
                boolean online = true;
                try {
                    socket.connect(sockaddr, 10000);
                }
                catch (IOException IOException) {
                    online = false;
        }
                if(!online){
            System.out.println("OFFLINE: Restarting Server..");
            //Runtime.getRuntime().exec("cmd /c start start.bat");
        }
                if(online){
                    System.out.println("ONLINE");
                }
                Thread.sleep(1 * 10000);
            }
        }
        catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

正如我在评论中提到的，根据Javadoc，isReachable的实现方式不允许您控制所选的端口。实际上，如果系统权限允许它这样做，它只会ping机器(ICMP请求)。

手动操作(例如，使用套接字)肯定会起作用，而且不会太复杂和/或更长：

SocketAddress sockaddr = new InetSocketAddress("cloudnine1999.no-ip.org", 43594);
// Create your socket
Socket socket = new Socket();
boolean online = true;
// Connect with 10 s timeout
try {
    socket.connect(sockaddr, 10000);
} catch (SocketTimeoutException stex) {
    // treating timeout errors separately from other io exceptions
    // may make sense
    online=false;
} catch (IOException iOException) {
    online = false;    
} finally {
    // As the close() operation can also throw an IOException
    // it must caught here
    try {
        socket.close();
    } catch (IOException ex) {
        // feel free to do something moderately useful here, eg log the event
    }

}
// Now, in your initial version all kinds of exceptions were swallowed by
// that "catch (Exception e)".  You also need to handle the IOException
// exec() could throw:
if(!online){
    System.out.println("OFFLINE: Restarting Server..");
    try {
        Runtime.getRuntime().exec("cmd /c start start.bat");
    } catch (IOException ex) {
         System.out.println("Restarting Server FAILED due to an exception " + ex.getMessage());
    }
}        

编辑:忘记处理IOException，这也意味着服务器不能工作，添加了

EDIT2:添加了close()可能抛出的IOException的处理

EDIT3:和exec()的异常处理