连接超时。为什么？

Question

运行此代码时出现异常。为什么？

线程“主”中的异常java.net.ConnectException：连接超时：connect

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.net.URL;

public class MainClass {

  public static void main(String[] args) throws Exception {

    System.setProperty("java.protocol.handler.pkgs", "com.sun.net.ssl.internal.www.protocol");

    URL url = new URL("https://www.verisign.com/");

    BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));

    String line;

    while ((line = in.readLine()) != null) {

      System.out.println(line);

    }

    in.close();

  }

}

例外：

Exception in thread "main" java.net.ConnectException: Connection timed out: connect

    at java.net.PlainSocketImpl.socketConnect(Native Method)

    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

    at java.net.Socket.connect(Socket.java:525)

    at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:550)

    at com.sun.net.ssl.internal.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:141)

    at sun.net.NetworkClient.doConnect(NetworkClient.java:163)

    at sun.net.www.http.HttpClient.openServer(HttpClient.java:394)

    at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)

    at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:272)

    at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329)

    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172)

    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:801)