.net HttpWebRequest: The underlying connection was closed: An unexpected error occurred on a send

Question

I am unable to connect to REST API for 1 of 2 URLs

iContact.com has 2 URLS for their REST API.

The following code will work for the first URL

"https://app.sandbox.icontact.com/icp/a/"

But will fail for the following URL

https://app.icontact.com/icp/a/

Code Details

• This is a console app
• The application was written in VB.net .Net Framework 4.5
• Nuget Packages Newtonsoft.JSON

Error: The underlying connection was closed: An unexpected error occurred on a send. SendFailure{4}

Troubleshooting:

• Confirmed is not a firewall issue by using chrome ARC app to test rest appi
• Able to ping the web site
• Sandbox URL is able to connect and retrive results
• Although the credentials provided are fake, you should be able to get a credential error instead of connection closed

Code Main Module:

Imports System.Net
Module MainModule
    Sub Main()
        Try
            Dim MyRequest As HttpWebRequest
            MyRequest = IContactManager.BuildJsonRequest
            Dim iContactSecurityInformation As ContactClass
            iContactSecurityInformation = IContactManager.GetiContactSecurityInformation(MyRequest)
        Catch ex As Exception

        End Try
    End Sub
End Module

Class:

Imports Newtonsoft.Json.Linq
Imports System.Net
Imports System.IO
Imports System.Web.Script.Serialization
Imports System.Text

Public Class ContactClass
    Public AppId As String
    Public BaseUrl As String
    Public Username As String
    Public Password As String
    Public AccountId As String
    Public ClientFolderId As String
    Public TestMode As Boolean
End Class

Public Class IContactManager
    Public Shared Function BuildJsonRequest() As HttpWebRequest
        Dim uri = New Uri(Convert.ToString(My.Settings.Base_URL + "a/"))
        'Production
        Dim request = DirectCast(WebRequest.Create(uri), HttpWebRequest)
        request.Method = "Get"
        request.Accept = "application/json"
        request.ContentType = "application/json"
        request.Headers.Add("Api-Version", "2.2")
        request.Headers.Add("Api-AppId", "fakeID")
        request.Headers.Add("Api-Username", "FakeUser")
        request.Headers.Add("Api-Password", "FakePassword")

        Return request
    End Function
    Public Shared Function GetiContactSecurityInformation(request As HttpWebRequest) As ContactClass
        Dim Acct As New ContactClass
        Dim a
        Try
            Using response = DirectCast(request.GetResponse(), HttpWebResponse)
                Using reader = New StreamReader(response.GetResponseStream())
                    Dim jsonData = reader.ReadToEnd()
                    Dim serializer = New JavaScriptSerializer()
                    a = serializer.Deserialize(Of ContactClass)(jsonData)
                End Using
            End Using
        Catch exc As System.Net.WebException
            Dim webResponse = TryCast(exc.Response, System.Net.HttpWebResponse)
            If webResponse IsNot Nothing AndAlso webResponse.StatusCode = System.Net.HttpStatusCode.Unauthorized Then
                Console.WriteLine("401")
            Else
                Throw
            End If
        End Try

        Return Acct
    End Function
End Class

Answer 1

I found the answer, you just need to use service point manager for the URL that is not working

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12