I’ve got this error and try to spend almost an hour to resolve this:

“the server committed a protocol violation section= responsestatusline” when I tried to get the response back from the payment gateway. It happens when you send HTTP Request one after another on the same page. The solution is to add unsafeheaderparsing to true in web.config and to seet keepAlive property to false from the http request it self

Web.Config

Calling Code:

   Private Function SendXML(ByVal strSend As String) As Boolean
        Dim blnSuccess As Boolean = False
        Dim objSendXML As XmlDocument
        Dim objRequest As HttpWebRequest
        Dim mywriter As StreamWriter
        Dim objResponse As HttpWebResponse
        Dim objReturnedXML As XmlDataDocument
        Dim objElementRoot As XmlElement
        Dim objElementTransaction As XmlNode
        Dim objElementCreditCardInfo As XmlNode
        Dim x As XmlNode

        Dim strApproved As String = String.Empty
        Dim blnCreditCardInfo As Boolean = False

        ' Must reset the variable incase of error
        Me._Paid = False

        objSendXML = New XmlDocument
        objRequest = WebRequest.Create(strPaymentURL)


        'if it is using proxy/behind proxy
        If (UseProxy And Not (String.IsNullOrEmpty(ProxyServer))) Then
            objRequest.Proxy = New System.Net.WebProxy(ProxyServer, True)

            'if there is credential
            If (UseDefaultCredential) Then
                objRequest.Proxy.Credentials = CredentialCache.DefaultCredentials
            Else
                objRequest.Proxy.Credentials = New NetworkCredential(UserName, Password)
            End If

        End If

        objRequest.Method = "POST"
        objRequest.ContentLength = strSend.Length
        objRequest.ContentType = "text/xml"

        'to solve protocol violation problem
        objRequest.KeepAlive = False