在尝试ping时,会抛出java.net.UnknownHostException.我不明白原因

Question

我写了下面的代码来试试ping.但是当我运行它时,会抛出以下异常:

java.net.UnknownHostException: http://localhost:8084/server/index.jsp
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
    at java.net.InetAddress$1.lookupAllHostAddr(Unknown Source)
    at java.net.InetAddress.getAddressFromNameService(Unknown Source)
    at java.net.InetAddress.getAllByName0(Unknown Source)
    at java.net.InetAddress.getAllByName0(Unknown Source)
    at java.net.InetAddress.getAllByName(Unknown Source)
    at java.net.InetAddress.getByName(Unknown Source)
    at Tester.main(Tester.java:10)

---

import java.net.InetAddress;

class Tester {
public static void main(String args[]) {
    try {
      InetAddress address = InetAddress.getByName("http://localhost:8084/server/index.jsp");
      boolean isReachable = address.isReachable(2000);
      if(isReachable)
        System.out.println("The address is reachable");
      else
        System.out.println("The address is not reachable");

    } catch(Exception exc) {
       exc.printStackTrace();
      }
}
}

为什么会这样？服务器正在运行,页面在Web浏览器中正常打开.

Answer 1

问题出在这一行:

InetAddress address = InetAddress.getByName(
        "http://localhost:8084/server/index.jsp");

该InetAddress.getByName(String)方法需要主机名.你给它一个URL字符串.该地址的主机名组件是"localhost".

如果要"ping"与URL关联的主机,则需要解析URL并提取主机名组件,如下所示:

String hostname = new URL(str).getHost();

但是,您需要处理URL格式错误的情况,或者没有主机名组件的情况.

我想你实际上是在尝试测试其他主机名,因为发送ICMP_PING请求"localhost"(通常127.0.0.1)是没有意义的.