Java HTTPUrlConnection超时不起作用

Question

我编写了一个程序,通过随机代理打开httpurlconnection到网站.我的httpurlconnection叫做conn.现在我知道,这其中的一些代理的可能太慢,所以我已经设置与连接至40000毫秒的超时conn.setConnectTimeout(40000)和conn.setReadTimeout(40000).

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();


    }

连接可能失败的原因有很多,因此在很多情况下我会到达最后一个catch-block并获得以下输出:

---

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实际通过时间:21009

---

所以我的问题是:我已经将超时设置为40000毫秒,但是在大约21000毫秒之后我得到了"连接超时" - 响应,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

看看你得到的例外:
最大的线索:你得到的是java.net.ConnectException 按照javadoc,java.net.ConnectException表示连接被远程拒绝,原因是没有进程正在监听端口.

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,则得到a java.net.SocketTimeoutException而不是a java.net.ConnectException.

那么,是什么造成的java.net.ConnectException？
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是所有配置都正确的快乐路径
• 在#4的情况下,我们得到一个java.net.SocketTimeoutException因为java进程能够建立连接(到代理端口),但是没有得到任何数据,因为目标主机的端口号无效
• 在#2,#5的情况下,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) .... ....

结论:

• 您尝试连接的某些代理必须关闭.因此java进程抛出java.net.ConnectException
• 最好java.net.ConnectException将代理捕获并标记为无效/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.