连接超时。 为什么？

运行此代码时出现exception。 为什么？

线程“main”中的exceptionjava.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.(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

你应该看看的事情：

• 你能ping主持人吗？
• 你可以使用网络浏览器连接到http://www.verisign.com吗？
• 你可以使用网络浏览器连接到https://www.verisign.com吗？
• 你能用你的程序连接到http://www.verisign.com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。