ConnectTimeout是否不总是阻止从inputstream读取？

Question

In my application, I open UrlConnections, and I set connection timeout. Sometimes, the timeout is thrown, but the inputstream is still readable (and do contain data)

I successfully reproed this using the following code:

    System.setProperty("http.keepAlive", "false");

    long length = 0;

    while (length == 0) {
        HttpURLConnection connection = null;
        try {
            connection = (HttpURLConnection) (new URL("http://www.worldofwargraphs.com").openConnection());
            connection.setConnectTimeout(1); // 1ms
            connection.connect();
        } catch (IOException ex) {
            try {
                byte[] buf = new byte[8196];
                try (InputStream is0 = connection.getInputStream(); InputStream is = new BufferedInputStream(is0, 8196)) {
                    if (is0 != null) {
                        int ret = 0;
                        while ((ret = is.read(buf)) > 0) {
                            length += ret;
                        }
                    }
                }
            } catch (IOException ex2) {
                Logger.getLogger(JavaApplication6.class.getName()).log(Level.SEVERE, null, ex2);
            }
        }
    }

    System.out.println(length);

As you can see in this code, I try to open a connection with a small timeout (1ms) to make sure that the connection timeouts. Then I try to read the inputstream

The thing is that, sometimes when trying to read the stream I get a java.net.SocketTimeoutException: connect timed out (which is what I would expect), but the loop sometimes ends, displaying the number of bytes read (32912)

Could anyone explain me why this second behavior sometimes happens ? I tried to google it, but found nothing about this.

Thanks

Answer 1

Your ridiculously short connect timeout expired, but the connection subsequently completed, so you were able to read. Note that setting a connection timeout doesn't set a read timeout, so the read blocked until data was available.

EDIT: In any case your code is wrong. You should set a realistic connect timeout and close the socket if you get it. Continuing to the read code after a connect exception doesn't make any sense.