I have a setup where multiple IPs can be configured for a network card
to allow multiple server programs binding on a port (80) each with their
own IPs.

  I want to invoke a HttpWebRequest from a specific IP that corresponds
with a given server.  How do I tell HttpWebRequest which IP to request
from?

here is a code snip of setting up a request:

   HttpWebRequest httpWebRequest =
HttpWebRequest)WebRequest.Create(requestUri);
   httpWebRequest.KeepAlive = false;
   WebProxy webProxy = WebProxy.GetDefaultProxy();
   webProxy.BypassProxyOnLocal = true;
   httpWebRequest.Proxy = webProxy;

   HttpWebResponse httpWebResponse;
    try
    {
        httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
    }
    catch (WebException webException)
    {
        httpWebResponse = (HttpWebResponse)webException.Response;
    }
    WebHeaderCollection responseHeaders = httpWebResponse.Headers;
    byte[] responseHtml = new byte[0];

    if(httpWebResponse.ContentLength > 0)
    {
         Stream httpWebResponseReader =
httpWebResponse.GetResponseStream();

etc
etc


thanks.

Hey Andrew,

I just posted exactly the same question... I guess I should have read the
threads beforehand.

Andrew, did you get a response or find a solution in the meantime?

Thanks, Christoph

Christoph Wienands wrote:

A new feature introduced in .NET 2.0 allows you to do that. See
http://msdn2.microsoft.com/library/ms144146(en-us,vs.80).aspx

Cheers,

Joerg Jooss wrote:
Thank you, that does look like a possibility.  However, how would I
assign a servicepoint to a httpwebrequest, if the
httpwebrequest.servicepoint property is read only?  Could you give a
code snip outlining how to create a servicepoint with a delegated
endpoint and how to assign that to a httpwebrequest? thanks!

Andrew Kibler wrote:

You don't and can't create ServicePoints -- that's being taken care of
by the framework. Use ServicePointManager to obtain a ServicePoint for
a given URI and attach your delegate to this object.

static void Get(Uri uri)
{
  HttpWebRequest request = (HttpWebRequest) WebRequest.Create(uri);
  request.UserAgent =
    "Mozilla/5.0 (Windows; U; Windows NT 5.1; de-DE; rv:1.7.8) " +
    "Gecko/20050511 Firefox/1.0.4";
  ServicePoint servicePoint =
    ServicePointManager.FindServicePoint(uri);
  servicePoint.BindIPEndPointDelegate = new BindIPEndPoint(Bind);

  using (MemoryStream memoryStream = new MemoryStream(0x10000))
  using (HttpWebResponse response =
   (HttpWebResponse) request.GetResponse())
  using (Stream responseStream = response.GetResponseStream())
  {
    // Add a breakpoint on the next line. When the breakpoint is
    // being hit, do a "netstat -p tcp" on a command line and
    // verify that port 8888 is being used.
    byte[] buffer = new byte[0x1000];
    int bytes;

    while ((bytes = responseStream.Read(buffer, 0, buffer.Length)) > 0)
    {
      memoryStream.Write(buffer, 0, bytes);
    }

    string text = Encoding.UTF8.GetString(memoryStream.ToArray());
    Console.WriteLine(text);
  }
}

static IPEndPoint Bind(ServicePoint servicePoint, IPEndPoint  
  remoteEndPoint, int retryCount)
{
  IPAddress address = IPAddress.Parse("192.168.2.102");
  return new IPEndPoint(address, 8888);
}

Of course you need to change the IP address in the sample to one that
exists in your machine.

Cheers,

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