Use HTTP PUT Method To Upload Local File To Server?

In my current project, my client application first talk with the server and the server returned an upload url for me to upload a file, the url looks like this: [URL] Then I want to use HTTP PUT method to upload the local "c:pesult.cab" to the above loacation. How could I do this? And could anyone give me a detailed description about the whole uploading mechanism? When I use a ASP.NET upload control, I just click the browse button to locate my file and click submit, and on the server side, I just call the SaveAs() method of the upload control. Here is some code:

protected void UploadButton_Click(object sender, EventArgs e)
{
if(FileUploadControl.HasFile)
{
try
{
string filename = Path.GetFileName(FileUploadControl.FileName);
FileUploadControl.SaveAs(Server.MapPath("~/") + filename);
StatusLabel.Text = "Upload status: File uploaded!";
}
catch (Exception ex)
{
StatusLabel.Text = "Upload status: The file could not be uploaded. The following error occured: " + ex.Message;
}
}
}

Who is responsible for reading the file and sending it? What happens when I call FileUploadControl.SaveAs() method? Does the server pull the file from client, or the client push the file to the server? I know HTTP is text based, but my result.cab is not text, so is it Base64 encoded before being sent? How does HTTP PUT method work? Is it a client side push, or a server side pull? Or interaction of both like some kind of handshake?