Java HTTPUrlConnection超时不起作用

我写了一个程序,通过随机代理打开一个网站的httpurl连接.我的httpurlconnection被称为conn.现在我知道,有些代理可能太慢,所以我已经使用conn.setConnectTimeout(40000)和conn.setReadTimeout(40000)将连接的超时设置为40000毫秒.

这样做后,我得到这个代码：

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();


    }

有连接可能会失败的原因,所以在很多情况下,我得到最后一个catch块并得到以下输出：

消息：连接超时：连接MyTimeout：40000实际通过时间：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通过的实际时间：21010

消息：连接超时：连接MyTimeout：40000通过的实际时间：21009

所以我的问题是：我将超时设置为40000毫秒,但是在大约21000毫秒之后我得到一个“连接超时” – 响应,你们有没有知道为什么呢？

编辑：im使用windows 7和我现在添加e.printStackTrace()到catch块,像注释中所说.感谢到目前为止.现在的输出是(示例)：

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

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)

+------------+------------+----------------+------------------+---------------------------------+ 
   | 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       |
   +------------+------------+----------------+------------------+---------------------------------+