VB。 NET：请求被中止：无法创建 SSL/TLS 安全通道

Question

I have an application coded in VB.net that has this method of accessing Webservice, i have this error and after searching fixes i still have no luck.

Error: The request was aborted: Could not create SSL/TLS secure channel.

    'ServicePointManager.Expect100Continue = False
    'ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls

    Dim request As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)

    Dim ErrMsg As String = String.Empty

    Try

        Dim response As WebResponse = request.GetResponse()

        Using responseStream As Stream = response.GetResponseStream()
            Dim reader As New StreamReader(responseStream, Encoding.UTF8)

            Return reader.ReadToEnd()
        End Using
    Catch ex As WebException

        ErrMsg = ex.Message.ToString
        MsgBox(ErrMsg)

        Dim errorResponse As WebResponse = ex.Response
        Using responseStream As Stream = errorResponse.GetResponseStream()
            Dim reader As New StreamReader(responseStream, Encoding.GetEncoding("utf-8"))
            ' log errorText
            Dim errorText As [String] = reader.ReadToEnd()
        End Using
        Throw
    End Try

This is my code and I'm using VS2015 and Windows 10.

All help are really appreciated. TIA

Answer 1

Obviously the URL you're calling requires TLS 1.1 or TLS 1.2 .

You can enable TLS 1.1 or TLS 1.2 by setting the security-protocol with ServicePointManager.SecurityProtocol :

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

.NET 4.0 supports up to TLS 1.0 while .NET 4.5 or higher supports up to TLS 1.2
For reference:

• Default SecurityProtocol in .NET 4.5
• Are there .NET implementation of TLS 1.2?

Answer 2

I'm going to add something here in case it helps others. I have to support some legacy code that is written in VB.Net and targets .NET Framework 4.6.1. The same piece of code runs in both an .exe, and in IIS as a web page.

In the website, this call:

Dim dataStream As Stream = request.GetRequestStream()

would throw this exception

The request was aborted: Could not create SSL/TLS secure channel.

but it worked fine in the .exe.

Forcing the TLS protocol fixed it in the website.

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

Of course if the host ever deems TLS 1.2 unworthy I'll have to fix/recompile/redeploy, but it solved the error for now.

Answer 3

for vb.net 4.0 this worked for me: ServicePointManager.SecurityProtocol = DirectCast(&HC0 Or &H300 Or &HC00, SecurityProtocolType)