java.net.SocketException:网络不可达:连接

2022-01-19 00:00:00 sockets exception network-programming java

我正在尝试使用此方法从 Web 服务器下载 xml 文本文件:

I am trying to download a xml text file from a web server using this method:

static void download (String url , String fileName) throws IOException{

            FileWriter xmlWriter;
            xmlWriter = new FileWriter(fileName);
            System.out.println("URL to download is : " + url);

            // here Exception is thrown/////////////////////////////////
            BufferedReader inputTxtReader = new BufferedReader
                        (new BufferedReader(new InputStreamReader(addURL.openStream())));
            ////////////////////////////////////////////////////////

            String str ;
            String fileInStr = "";

            str = inputTxtReader.readLine();

            while (!(str == null)  ){///&& !(str.equals("</tv>"))
                fileInStr += (str + "
");
                str = inputTxtReader.readLine();
            }

            xmlWriter.write(fileInStr);
            xmlWriter.flush();
            xmlWriter.close();
            System.out.println("File Downloaded");
}

有时会抛出此异常(我指定的是代码):

Sometimes this exception is thrown (where I specified is code):

java.net.SocketException: Network is unreachable: 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.Socket.connect(Socket.java:518)
    at java.net.Socket.connect(Socket.java:468)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:389)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:516)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:233)
    at sun.net.www.http.HttpClient.New(HttpClient.java:306)
    at sun.net.www.http.HttpClient.New(HttpClient.java:318)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:788)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:729)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:654)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:977)
    at java.net.URL.openStream(URL.java:1009)
    at MessagePanel.download(MessagePanel.java:640)
    at WelcomThread.run(MainBody2.java:891)

请指导我

谢谢大家.

推荐答案

您正面临连接中断.这是否发生在 3G、WiFi 或计算机上的普通"连接中?

You are facing a connection breakdown. Does this happen in 3G, WiFi or "plain" connection on a computer?

无论如何，在编写应用程序时，您必须假设连接可能会不时丢失.例如，对于手机，这种情况在地铁、地下室等中经常发生.对于 PC 应用程序，这种情况不太常见，但有时会发生.

Anyway, you must assume that the connection may be lost from time to time, when writing your app. For example, with mobiles, this happens frequently in the tube, in basements, etc. With PC apps, this is less frequent but occurs sometimes.

重试可能是一个很好的解决方案.并且说明网络的干净错误消息目前也不可用.

A retry can be a good solution. And a clean error message that explains the network is not available at this moment too.

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