Question

我已经编写了一个程序，通过随机代理打开httpurlconnection到网站。我的httpurlconnection名为 conn 。现在我知道，其中一些代理可能太慢，所以我使用conn.setConnectTimeout(40000)和conn.setReadTimeout(40000)将连接超时设置为40000毫秒。

这样做后，我得到了这段代码：

long diff = 0;
    long starttime = 0;
    long endtime = 0;

    try
    {
        starttime = System.currentTimeMillis();
        conn.connect();

        endtime = System.currentTimeMillis();

        diff = endtime - starttime;

        if (endtime <= starttime + conn.getConnectTimeout())
        {
            //Trying to read sourecode
            InputStreamReader isrConn = new InputStreamReader(conn.getInputStream());
            BufferedReader brConn = new BufferedReader(isrConn);

            line = brConn.readLine();

            while (line != null)
            {

                response += line + "\t";
                try
                {
                    line = brConn.readLine();
                } catch (IOException e)
                {
                    printError("Reading sourcecode failed.");
                }

            }
        }
        else
        {
            response = "blabla.";
        }




    // If conn.connect failed   
    } catch (IOException e)
    {
        endtime = System.currentTimeMillis();
        diff = endtime - starttime;

        response = "Message: "+e.getMessage() +" MyTimeout:"+ conn.getConnectTimeout() +" Actual time passed:  "+ diff;
               e.printStackTrace();


    }

连接失败的原因有多种，所以在很多情况下我会到达最后一个catch-block并得到以下输出：

消息：连接超时：连接MyTimeout：40000实际传递时间：21012

消息：连接超时：连接MyTimeout：40000实际传递时间：21016

消息：连接超时：连接MyTimeout：40000实际传递时间：21010

消息：连接超时：连接MyTimeout：40000实际传递时间：21009

所以我的问题是：我已经将超时设置为40000毫秒，但是我得到一个＆＃34;连接超时＆＃34; - 响应约21000毫秒后，你们中的任何人都知道为什么会这样吗？

编辑：即时通讯使用Windows 7，我现在将e.printStackTrace（）添加到catch块，就像在评论中说的那样。谢谢到目前为止。现在的输出是（例子）：

java.net.ConnectException: Connection timed out: connect
    at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
    at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
    at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at sun.net.NetworkClient.doConnect(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient$1.run(Unknown Source)
    at sun.net.www.http.HttpClient$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.net.www.http.HttpClient.privilegedOpenServer(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.<init>(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
    at TestThread.getSourcePage(TestThread.java:361)
    at TestThread.aChecker(TestThread.java:216)
    at TestThread.getNextProxy(TestThread.java:169)
    at TestThread.getNextC(TestThread.java:157)
    at TestThread.aChecker(TestThread.java:273)
    at TestThread.getNextProxy(TestThread.java:169)
    at TestThread.aChecker(TestThread.java:295)
    at TestThread.getNextProxy(TestThread.java:169)
    at TestThread.getNextC(TestThread.java:157)
    at TestThread.run(TestThread.java:103)
    at java.lang.Thread.run(Unknown Source)

Message: Connection timed out: connect MyTimeout:40000 Actual time passed:  21015

Answer 1

查看您遇到的例外情况：
最大的线索：你得到java.net.ConnectException 根据javadoc，java.net.ConnectException表示由于没有进程正在侦听端口等原因而远程拒绝连接。

public class ConnectException
extends SocketException

Signals that an error occurred while attempting to connect a socket to a remote address and port. 
Typically, the connection was refused remotely (e.g., no process is listening on the remote 
address/port)

您在HttpUrlConnection中配置的内容：
连接超时（假设远程端口接受连接）。如果连接超时到期，您将获得java.net.SocketTimeoutException而不是java.net.ConnectException。

那么，导致java.net.ConnectException的原因是什么？
我尝试了以下测试用例：

   +------------+------------+----------------+------------------+---------------------------------+ 
   | Valid Host | Valid Port | Valid Proxy IP | Valid Proxy Port | Exception                       | 
   +------------+------------+----------------+------------------+---------------------------------+ 
#1 | yes        | yes        | -NA-           | -NA-             | -- none --                      |
#2 | yes        | no         | -NA-           | -NA-             | java.net.ConnectException       |
   +------------+------------+----------------+------------------+---------------------------------+ 
#3 | yes        | yes        | yes            | yes              | -- none --                      |
#4 | yes        | no         | yes            | yes              | java.net.SocketTimeoutException |
#5 | yes        | yes        | yes            | no               | java.net.ConnectException       |
   +------------+------------+----------------+------------------+---------------------------------+

案例＃1，＃3是所有配置正确的快乐路径
在＃4的情况下，我们得到java.net.SocketTimeoutException因为java进程能够建立连接（到代理端口），但是由于目标主机的端口号无效而无法读取任何数据
如果＃2，＃5我们得到java.net.ConnectException，因为java进程尝试写入/读取的端口无效
对于没有进程正在侦听java进程尝试连接的端口的情况，连接超时值不适用。这就是你在超时到期之前得到ConnectException的原因

Message: Connection refused: connect MyTimeout:10000 Actual time passed: 6549 java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) .... ....

<强>结论：

您尝试连接的某些代理必须关闭。因此，java进程抛出了java.net.ConnectException
最好抓住java.net.ConnectException并将代理标记为无效/关闭

Answer 2

根据我的经验，HttpUrlConnection在名称解析期间不会超时。如果您的设备已缓存目标地址，则它将正确超时。

出于测试目的，请在代码中使用您的IP地址。

这通常发生在移动设备上。

Java HTTPUrlConnection超时不起作用

2 个答案: