Re: Some advice on dealing with a networking issue

Tom Anderson <>
Thu, 21 Jan 2010 22:57:07 +0000
On Thu, 21 Jan 2010, The Frog wrote:

There is a website, actually an ftp site with (surprise surprise!) files
on it. each week a new file is added. On my local network is a shared
folder that I need to keep updated with files from the FTP site. So far
so simple. Here's the issue: Due to a proxy server (simple
authentication where it requests a username and password to access the
internet) I can only access the FTP site via a web browser (eg/ Internet
Explorer, Firefox, etc...) and download the file(s) I want manually.
What is being done 'behind the scenes' so to speak is that the web
browser is using HFTP to download the file (FTP over HTTP). What I would
like to do is to write an application that can download these files for

Have a read of sections 2.3 and 3 in here:

You can do 'HFTP' with a normal URLConnection. To summarise that link (all
classes not from java.lang are from

SocketAddress proxyAddr = new InetSocketAddress("", 8080);
Proxy proxy = new Proxy(Proxy.Type.HTTP, proxyAddr);
URL url = new URL("");
URConnection conn = url.openConnection(proxy);

You mention that your proxy server requires authentication. If it's doing
this with the HTTP authentication mechanism, then you can, i believe,
cooperate with that using Authenticator:

String username;
String password;
Authenticator.setDefault(new Authenticator() {
  protected PasswordAuthentication getPasswordAuthentication() {
  // should really validate host and prompt/realm here to make sure it's the proxy
  return new PasswordAuthentication(username, password.toCharArray());

I don't think there's a way to do per-connection authentication with
standard JDK classes. Apache HttpClient can do it, though, so that would
be a cleaner option if you're willing to use an extra library and write
slightly more long-winded code.


You have now found yourself trapped in an incomprehensible maze.

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