Question

我通过套接字编程将xml数据发送到服务器。我发现有时当服务器关闭并且客户端报告套接字超时时，我无法发送或接收。

我想处理此异常并尝试重新发送3到4次。我应该使用Thread.sleep，写入循环，还是有更好的方法？

   private String sendRequestToChannel(String request) {

    String xmlData = null;
    BufferedReader rd = null;
    BufferedWriter bw = null;
    String line = null;
    String lineSep = null;
    String data = null;
    StringBuffer serverData = null;


    try {

        Socket cliSocket = new Socket();

        cliSocket.connect(new InetSocketAddress(HOST, PORT), SOCKET_TIMEOUT);

        bw = new BufferedWriter(new OutputStreamWriter(cliSocket.getOutputStream()));

        bw.write("POST " + PATH + " HTTP/1.0\r\n");
        bw.write("Host: " + HOST + "\r\n");
        bw.write("Content-Length: " + request.length() + "\r\n");
        bw.write("Pragma: cache\r\n");
        bw.write("Cache-Control: private, must-revalidate\r\n");
        bw.write("Content-Type: application/x-www-form-urlencoded\r\n");
        bw.write("\r\n");
        bw.write(request);
        bw.flush();

        rd = new BufferedReader(new InputStreamReader(cliSocket.getInputStream()));

        System.out.println("Step 4 : Getting Input Stream");
        serverData = new StringBuffer("");


        lineSep = System.getProperty("line.separator");
        while ((line = rd.readLine()) != null) {
            serverData.append(line);
            serverData.append(lineSep);
        }

        data = serverData.toString();
        int index = data.indexOf("<");

        if (index != -1) {
            xmlData = data.substring(index);

        } else {
            System.out.println("\r\n \r\n  XML Data Not Retrived");
        }


    } catch (java.net.UnknownHostException uh) {
        uh.printStackTrace();
        System.out.println("$$$$$$$$$$$$  in sendRequestToChannel : UnknownHostException " + uh.getMessage());
        return "   in sendRequestToChannel : UnknownHostException " + uh.toString();
    } catch (IOException ioe) {
        ioe.printStackTrace();
        System.out.println("$$$$$$$$$$$$  in sendRequestToChannel :  IOException " + ioe.getMessage());
        return " in sendRequestToChannel :   IOException " + ioe.toString();
    } catch (Exception e) {
        e.printStackTrace();
        System.out.println("$$$$$$$$$$$$  in sendRequestToChannel :  Exception " + e.getMessage());
        return " in sendRequestToChannel :  Exception " + e.toString();
    } finally {
        try {
            if (bw != null) {
                bw.close();
            }
        } catch (IOException ex) {
            Logger.getLogger(SA_Caesar.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            if (rd != null) {
                rd.close();

            }
        } catch (IOException ex) {
            Logger.getLogger(SA_Caesar.class.getName()).log(Level.SEVERE, null, ex);



        }

        bw = null;
        rd = null;
        line = null;
        lineSep = null;
        data = null;
        serverData = null;

    }
    return xmlData;
}

Answer 1

当远程服务出现故障时，应用程序面临的最大问题是，根本没有可以预测何时返回

。

您已经在使用TCP连接，在面对短期无法访问的服务时会重试，但是当TCP宣布连接失效时，您实际上并没有通过自动尝试重新建立连接来提高可靠性连接。例如，如果远程服务器需要两天时间才能返回，那么您的应用程序是否能够像从未停止过一样行事？在停电期间，所有必要的数据是否都会排队？连接系统的语义是否会在周末的故障中得到保留？如果远程服务停机5天怎么样？

从系统角度来看，您可以做的最好的事情是通知操作员有一个需要注意的故障。这就是我们在可预见的未来仍然拥有运营商和意愿的原因。

如何为可靠的传输重试丢失的连接？

1 个答案: