Visual Basic HttpWebRequest 获取 SendFailure 错误

如何解决Visual Basic HttpWebRequest 获取 SendFailure 错误

我已经尝试了这里的许多建议，但仍然收到 SendFailure 错误。

这是代码 - 它是直接的网络请求

Dim request As HttpWebRequest
Dim webAddress As String = "https://www.google.com"
'webAddress = "https://www.yahoo.com"

ServicePointManager.SecurityProtocol = Net.SecurityProtocolType.Tls
ServicePointManager.ServerCertificateValidationCallback = _
        New RemoteCertificateValidationCallback(AddressOf AcceptAllCertifications)

request = DirectCast(WebRequest.Create(webAddress),HttpWebRequest)
request.ReadWriteTimeout = 5500
request.Timeout = 5500
request.KeepAlive = False
request.Method = "GET"

Using response = request.GetResponse()
        sr = New StreamReader(response.GetResponseStream())
        activated = sr.ReadToEnd()
        Console.WriteLine("activated says: " + activated)
        resp = Split(activated,",")
        sr.Close()
        response.Close()
End Using

对于谷歌请求，我在“激活”变量中获取页面内容，并在证书回调函数中获得访问命中。

对于雅虎请求，我立即收到 WebException 状态 4：SendFailure。证书回调函数没有命中。

为什么会这样？我想不明白。我使用的是 VisualStudio 2010。