Re: HTTP connection doesn't work on digg?

From:
Ian Wilson <scobloke2@infotop.co.uk>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 16 Apr 2007 14:20:36 +0100
Message-ID:
<4623782e$0$21840$db0fefd9@news.zen.co.uk>
Russell Glasser wrote:

I'm trying to familiarize myself with the method of connecting to web
sites with Java. I've written a simple program to connect to a page
at a given URL, but I've noticed it behaves differently for different
sites.

Here's some code which I have stripped of most of the extra stuff just
to highlight the problem:

----

    public void connTest (String addr)
    {
        try {
            System.out.println("Trying to connect to "+addr);
            URL u = new URL(addr);
            HttpURLConnection conn = (HttpURLConnection) u.openConnection();
            conn.connect();
            InputStream is = conn.getInputStream();
            System.out.println("Input stream is open...");
            is.close();
            conn.disconnect();
        } catch (Exception e) {
            System.out.println ("Something's wrong");
        }
    }

----

Then to invoke it, I try:

    connTest("http://www.google.com");
    connTest("http://www.digg.com");

Here's the output:

Trying to connect to http://www.google.com
Input stream is open...
Trying to connect to http://www.digg.com

The first method call takes a few seconds, but then gives me what I
asked for (and then I can go ahead and print out all the html with a
reader). The second method call just hangs. As soon as it hits the
line "InputStream is = conn.getInputStream();" it's stuck. The same
thing happens if I try to get any other property, such as
getResponseCode.

I've tried this with several web sites and Digg is the only widely-
used site that gives me this problem. But I can open it in a browser
just fine. Am I doing something wrong?


1) You may not be waiting long enough, It can take minutes for DNS
resolution to give up or for conection attempts to fail. Try
connTest("http://imaginary.example.com") and see what result you get and
how long it takes.

2) Your exception handling discards all the useful information in the
exception. I'd at least print e.getMessage() or a stack trace.

3) Popular free services (like Google) often take measures to prevent
use of their normal HTTP service by anything other than a human clicking
a web-browser. Sometimes they have an API and a registration process for
software authors. Maybe Digg is even more intolerant than Google of what
they perceive as inappropriate use?

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