HTTP 的绕过防盗链接 纵一苇之所如

代理通过http取这个资源的时候，要在在request Header上加入一个被允许的 Referere，一般是那个网站的host

判断浏览器请求时HTTP头的Referer字段的值，这个值在asp.net里面可以用 Request.UrlReferrer属性取得

 Dim myHttpWebRequest As HttpWebRequest = DirectCast(WebRequest.Create(BaseUrl & PDFLinks(i)), HttpWebRequest)
                    myHttpWebRequest.ContentType = "text/html"
                    myHttpWebRequest.Method = "GET"
                    myHttpWebRequest.Referer = "http://ssssss.com"
                    Dim FStream As FileStream = New FileStream(pathPageName, FileMode.Create)
                    Dim myStream As Stream
                    myStream = myHttpWebRequest.GetResponse().GetResponseStream()
                     Dim btContent As Byte() = New Byte(511) {}
                    Dim intSize As Integer = 0
                    intSize = myStream.Read(btContent, 0, 512)
                    While intSize > 0
                        FStream.Write(btContent, 0, intSize)
                        intSize = myStream.Read(btContent, 0, 512)
                    End While
                    '关闭流
                    FStream.Close()
                    myStream.Close()