"The underlying connection was closed: An unexpected error occurred on a send." With SSL Certificate

Question

Issue : I get this exception "THE UNDERLYING CONNECTION WAS CLOSED: AN UNEXPECTED ERROR OCCURRED ON A SEND" in my logs and it is breaking our OEM integration with our email marketing system at random times varying from [1hour - 4 hours]

My website is hosted on a windows server 2008 R2 with IIS 7.5.7600. This website has a large number of OEM components and comprehensive dashboard. Everything works fine with all the other elements of the website except with one of our email marketing component which we are using as an iframe solution within our dashboard. The way it works is, I send a httpWebRequestobject with all the credentials and i get a url back which i put in an iframe and it works. But it only works for some time [1 hour - 4 hours ]and then i get the below exception "THE UNDERLYING CONNECTION WAS CLOSED: AN UNEXPECTED ERROR OCCURRED ON A SEND" and even if the system tries to get the URL from the httpWebRequest it fails with the same exception. The only way to make it work again is to recycle the application pool or anything is edited in web.config. I am really exhausted all the option that i could think of.

Option tried

Explicitly added, keep-alive = false

keep-alive = true

Increased the time out : <httpRuntime maxRequestLength="2097151" executionTimeout="9999999" enable="true" requestValidationMode="2.0" />

I have uploaded this page to a non SSL website to check if the SSL certificate on our production server is making the connection to drop some how.

Any direction toward resolution is greatly appreciated.

Code :

Public Function CreateHttpRequestJson(ByVal url) As String
    Try
        Dim result As String = String.Empty
        Dim httpWebRequest = DirectCast(WebRequest.Create("https://api.xxxxxxxxxxx.com/api/v3/externalsession.json"), HttpWebRequest)
        httpWebRequest.ContentType = "text/json"
        httpWebRequest.Method = "PUT"
        httpWebRequest.ContentType = "application/x-www-form-urlencoded"
        httpWebRequest.KeepAlive = False
        'ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3

        'TODO change the integratorID to the serviceproviders account Id, useremail 
        Using streamWriter = New StreamWriter(httpWebRequest.GetRequestStream())
            Dim json As String = New JavaScriptSerializer().Serialize(New With { _
            Key .Email = useremail, _
            Key .Chrome = "None", _
            Key .Url = url, _
            Key .IntegratorID = userIntegratorID, _
            Key .ClientID = clientIdGlobal _
            })

            'TODO move it to the web.config, Following API Key is holonis accounts API Key
            SetBasicAuthHeader(httpWebRequest, holonisApiKey, "")
            streamWriter.Write(json)
            streamWriter.Flush()
            streamWriter.Close()

            Dim httpResponse = DirectCast(httpWebRequest.GetResponse(), HttpWebResponse)
            Using streamReader = New StreamReader(httpResponse.GetResponseStream())
                result = streamReader.ReadToEnd()
                result = result.Split(New [Char]() {":"})(2)
                result = "https:" & result.Substring(0, result.Length - 2)
            End Using
        End Using
        Me.midFrame.Attributes("src") = result
    Catch ex As Exception
        objLog.WriteLog("Error:" & ex.Message)
        If (ex.Message.ToString().Contains("Invalid Email")) Then
            'TODO Show message on UI
        ElseIf (ex.Message.ToString().Contains("Email Taken")) Then
            'TODO Show message on UI
        ElseIf (ex.Message.ToString().Contains("Invalid Access Level")) Then
            'TODO Show message on UI
        ElseIf (ex.Message.ToString().Contains("Unsafe Password")) Then
            'TODO Show message on UI
        ElseIf (ex.Message.ToString().Contains("Invalid Password")) Then
            'TODO Show message on UI
        ElseIf (ex.Message.ToString().Contains("Empty Person Name")) Then
            'TODO Show message on UI
        End If
    End Try
End Function


Public Sub SetBasicAuthHeader(ByVal request As WebRequest, ByVal userName As [String], ByVal userPassword As [String])
    Dim authInfo As String = Convert.ToString(userName) & ":" & Convert.ToString(userPassword)
    authInfo = Convert.ToBase64String(Encoding.[Default].GetBytes(authInfo))
    request.Headers("Authorization") = "Basic " & authInfo
End Sub`

Answer 1

For me it was tls12:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;