C#, WebClient and Windows Server 2008

Question

I have a big problem with WebClient class on Windows Server 2008. I have small code that downloads data from web using WebClient.DownloadFile/DownloadData method. Everything works ok on Windows 2003 and Windows 7, but not on Windows Server 2008. On 2008 I get a very low speed (about 5kb/s where normaly I have about 1mb/s).

I did some research and checking: - problem only exists on couple of servers (not every one, one of it is newconnect.pl -> example file http://newconnect.pl/index.php?page=get_ebi_file&id=6023), - I checked a couple of servers with 2008 - diffrent machines, different network connections - problem existed at each one. - I tried the trick with setting proxy to null or empty - didnt help - I used wireshark to check what is wrong - I didnt notice anything weird, just lower speed. - if I create a virtual machine with windows 2003 at windows 2008 and install downloader at win2k3 it works ok.

Thanks for help.

Code:

class Program
{
    static void Main(string[] args)
    {
        string file1 = "http://newconnect.pl/index.php?page=get_espi_file&file=zal_7161967.pdf";
        string file2 = "http://newconnect.pl/index.php?page=get_espi_file&file=zal_7163706.pdf";

        WebClient wc = new WebClient();
        wc.Proxy = null;
        Console.WriteLine(DateTime.Now.ToString());
        wc.DownloadData(file1);
        Console.WriteLine(DateTime.Now.ToString());
        wc.DownloadData(file2);
        Console.WriteLine(DateTime.Now.ToString());

        Console.Read();
    }
}

}

Answer 1

I have a blog post on my blog that goes into performing multiple http requests using HttpWebRequest and asynchronous class (for performance). HttpWebRequest - Asynchronous Programming Model/Task.Factory.FromAsyc

Noe you may not be keen to use async programming but nonetheless there are some settings you need to change in order to get more than 2 simultaneous http class and that's also explained in the post I've linked to above. Specifically, you need to modify the ServicePointManager's DefaultConnectionLimit property (which is set to 2 per domain by default).

So if you're calling the same domain multiple times, then changing this value to a larger number will make a huge difference in the performance you're seeing.

Since making http requests and downloading files are purely I/O workloads, you should seriously look at using asynchronous calls in your case too. There are multiple examples/styles I've shown in the post that you could use. Even WebClient uses the Event based Async programming model, that you might want to look at using.