连接超时.为什么？

Question

运行此代码时出现异常.为什么？

线程"main"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)
    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)
    at com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnectionOldImpl.getInputStream(HttpsURLConnectionOldImpl.java:204)
    at java.net.URL.openStream(URL.java:1010)
    at https.ssl.MainClass.main(MainClass.java:13)

Answer 1

你应该看看的东西:

• 你ping能主持人吗？
• 你可以连接到http://www.verisign.com使用网络浏览器吗？
• 你可以连接到https://www.verisign.com使用网络浏览器吗？
• 你能连接到http://www.verisign.com你的程序吗？
• 你能使用你的程序连接任何东西吗？

您的问题可能与防火墙有关.我的第一个猜测是你没有设置正确的环境变量或Java系统属性来告诉JVM使用本地代理服务器来传出HTTP/HTTPS请求.